Follow GPX track

Yes the 520 allows you upload a GPX, TCX or FIT file that contains a course and follow it.

Thank you aweatherall for your response,

How does it look? that following. is it turn by turn? (What i think is not possible, because forrest tracks are not routable)
Do you know if there is a example video somewhere on the net, with shows this kind of track following

I have done exactly this with off-road rides. You don't get any navigation prompts as such, just a line on the map page to follow. If you deviate off course for any reason the device will beep at you and display the message "off course" buts that's all. It's up to you to get "on course" and find the red line again. This can be an issue if you are forced to deviate by an impassable obstruction, say. Works better if you load some custom maps of the area you are riding as they will show you some features such as woods, paths etc. Search for the how-to on this (it's easy) - DC Rainmaker has done a guide.

I'd also caution you on the battery life of this device. Navigation with the latest firmware installed sees my unit flat after 4 hours and it's not just me, see the thread about it on here. Caveat Emptor.

Thanks Lardtm,
I think this is the how to you referring to,
https://www.dcrainmaker.com/2013/05/download-garmin-705800810.html

and thank you for the warning about the firmware update ;)

The 520 can not generate turn directions from a routable map. It uses cue sheet entries that have been added to the source file for turn directions. RideWithGPS generates cues for many trails. You can manually add cues in RWGPS too. You need to output a TCX file from RWGPS to get the cue list included in the file.

I create routes on my mobile with OSMAND+, share them with the garmin connect app an upload them to my 520. This routes are very usable and have turn by turn on the 520. Only thing is that you need a internet connection.

The continuous issues with most Garmin firmware updates is very frustrating when you just want to jump on the bike and ride without having to deal with numerous problems. But many of us manage to do this with a few simple tricks.

1, Disable automatic firmware updates from both the Garmin website and app. (there are lots of forum topics on how to do this)
2. Only update (manually) after a firmware version has been available for a number of months without reported issues, this would rule out recent 12.2, 12.3, 12.4 & 12.5). If subsequent updates have been released in those few months then you can still get the known (reported) good one via the rollback method (see 3.).
3. If you are already stuck with a dud update then roll back to a known good version (or at least a less bad one). Again there are numerous posts on how to do this and ensure you have a backup of your settings in case they get wiped during an update / rollback. I stayed on 9.1 for a long time and it was trouble free for me. When 12.1 was released it had a feature or two I thought would be useful so after a few months without negative reports I undated and have stayed there since. Only update if an included feature is something you will find useful otherwise just sit on the version you have.
4. These are small devices with limited memory and processing power, every feature / option / connection you enable will chew into the memory and processing capability until it overloads something and will crash, they also all use more battery to support the extra processing power required. Ask yourself if you really need all the things you enable / connect to and reduce them to a minimum and this will give you a more resilient device that uses less battery. I have a 2 year old 520 with a couple of sensors, mostly follow courses and will get near 20 hours from a battery charge. Spend a little time in understanding the options / features on the device so you can configure it according to your needs rather than accepting the default options / settings.

With this approach you can have a mostly trouble free device, Good Luck

The continuous issues with most Garmin firmware updates is very frustrating when you just want to jump on the bike and ride without having to deal with numerous problems. But many of us manage to do this with a few simple tricks.

1, Disable automatic firmware updates from both the Garmin website and app. (there are lots of forum topics on how to do this)
2. Only update (manually) after a firmware version has been available for a number of months without reported issues, this would rule out recent 12.2, 12.3, 12.4 & 12.5). If subsequent updates have been released in those few months then you can still get the known (reported) good one via the rollback method (see 3.).
3. If you are already stuck with a dud update then roll back to a known good version (or at least a less bad one). Again there are numerous posts on how to do this and ensure you have a backup of your settings in case they get wiped during an update / rollback. I stayed on 9.1 for a long time and it was trouble free for me. When 12.1 was released it had a feature or two I thought would be useful so after a few months without negative reports I undated and have stayed there since. Only update if an included feature is something you will find useful otherwise just sit on the version you have.
4. These are small devices with limited memory and processing power, every feature / option / connection you enable will chew into the memory and processing capability until it overloads something and will crash, they also all use more battery to support the extra processing power required. Ask yourself if you really need all the things you enable / connect to and reduce them to a minimum and this will give you a more resilient device that uses less battery. I have a 2 year old 520 with a couple of sensors, mostly follow courses and will get near 20 hours from a battery charge. Spend a little time in understanding the options / features on the device so you can configure it according to your needs rather than accepting the default options / settings.

With this approach you can have a mostly trouble free device, Good Luck

Nice to have 20 hours off battery life! Can you please be more precise about your 520 settings? I am a new 520 owner, I have firmware 12.5 installed and the things I did;

1. Removed the useless maps (small screen and the maps are undetailed).
2. Removed the unused languages.
3. Turn the screen in nightmode? Or does daymode use less battery?
4. Add some ant+ sensors; speed, light, hart and cadans. Does ant+ sensors use a lot battery?
5. Installed gimport iq app, for sending interfree bluetooth gpx files from my phone to the device.
6. When riding, bluetooth is turned off.

"...Can you please be more precise about your 520 settings?.."

Of course might not be useful to you as some features that are big power users might also be the ones you want to use.

In general the biggest battery drainers are the backlight and phone connections. Set the backlight to the minimum you can live with, mine is 10% and turn off in 15 seconds, I have no problems reading the screen in most conditions and when riding at night (which I do a lot, sometimes all night) might still use the settings above or if I want to follow a complex route will use 10% and stays on.

I don't use phone connections at all.

I suspect a lot of the IQ apps are battery drainers, the technology is not mature, is script based so not too efficient and requires the developer to be skilled and competent which seems to be beyond the professional garmin developers so what hope for well meaning amateurs?.

Maps and navigation can be power consuming but it is possible to configure a minimal power use mode by turning off the "Turn Guidance" (Training>Courses>Course Options), it makes no difference, only there to support route prompts from GPS routes which does not work anyway. You can get the same with TCX routes without the overhead.

The installed world maps are useless but should be replaced with an OSM map of your area, sites like BBBike.org will allow a defined area to be selected to minimise the map size and some formats (Garmin OnRoad) are very efficient with a large area & small file size possible (it removes some map features which I at least don't miss, eg ground shading, street names, points of interest but keeps the actual roads).

I find Day Mode the best for day or night

"Incident Detection" is not reliable or worth the bother