Need advice from Forerunner 235 users

I'm only speaking from personal experience:

Technically the 235 can do all those things. For gym workouts, the built in HRM is not accurate for me. I've yet to find a device with a built in optical HRM which will be accurate for general gym workouts. There's just too much variation in the muscles and arm movements, and it throws the HRM out of whack.

For hiking, it's been just so-so. Some hikes have been ok, others have been bad. I ended up ordering a Fenix 5 because I do a lot of hiking and I'm hoping it's more reliable.

Again, just my experience, so take it with a grain of salt.

As far as Hiking, check out my Hike app.

For both Hiking and walking (there isn't a native "walk" app on the 23x devices, so you can also just use it for outdoor walking)

For me it's ok if I can take recovery times with a stopwatch in the gym and I can see more or less my heart rate when I'm doing weight lifting, it's a good compromise if it's not precise at all but I don't need the chest strap, because I can't workout with the strap, it's too annoying.
The other thing I need is that when I go hiking in the countryside, in the hills nearby or in mountain I can have the report in the garmin connect app about the route, the distance and altitude

If you think these three things are possible then I'll buy it

Thanks

Please be aware that the FR235 does not have a barometric altimeter. The altitude is GPS-based and thus less accurate. Many hardcore hikers find GPS-based altitude not accurate enough, so it's up to you to decide what level of accuracy you need.

For your gym workouts you can use the "Other" activity on the watch with a data screen set to show the timer and HR and just not save the activity at the end. But like was said above, a lot of flexing of the forearm muscles will effect how well the built in HRM works.

For the walking/hiking can't recommend the above mentioned Hike app enough. It works great on the FR235 and will register it appropriately in Garmin Connect.

I use Other for my gym workouts. I've set the the first data screen to four fields with heart rate, time of day, lap time, and total time.

For strength training, I hit the lap button after each set and then use the lap time as a timer for my rest before the next set. As for the heart rate, the OHR struggles during most lifting, but recovers between sets. Using my chest HR strap paired with the 235 would solve that (I think), but it's not important enough for me to bother with it.

For cardio, the OHR works well 95% of the time on the elliptical. Every once in a while it struggles to get a good lock, likely due to my grip on the handles.

Regarding hiking, I use the Hike app. It works really well for me. It is important to note that elevation is derived from the GPS signal, so it's not perfect. You can check the app out on the Connect IQ site. https://apps.garmin.com/en-US/apps/39d3b5e8-67db-4517-93a8-5ec485269635

Here is a link to a hike I did using the Hike app... https://connect.garmin.com/modern/activity/1189968641

Thank you all!
Last question, the watch doesn't have the barometric altimeter, without this sensor how much does it get wrong calculating the altitude?
I mean, with only GPS it's 20-50 meters wrong or something like 50-100 or 100-200 meters??
Just to have an idea

Thanks

Without a baro, it can be off on the watch itself (it depends on the terrain, based on what I've seen). When the activity is uploaded to Garmin Connect, "Elevation Correction" is applied, which I find often really helps.

In addition to Hike, I also wrote Hike2 (it's really Hike with a bunch of features added to it), which is for different devices with more memory, etc, including some with a baro. I'll often be wearing two watches - one with Baro and one without for testing just so I can compare things (if I make a change in Hike, I'll test it against Hike2 for example). From what I've seen, the one with baro(without elevation correction) and the one without a baro (but with the elevation correction), are very similar when it comes to elevation data on Garmin Connect.

Thanks, i saw your app already in some review in internet.
So based on your advices i'm choosing between vivoactive hr+ that has barometer altitude and the possibility to use Hike2 and a lot of profile sports and the forerunner 235.
For the things i have to do i'm more oriented to the vivoactive hr+ but the square screen makes me struggle and makes me want to buy the forerunner 235.

I will see now between these 2.

Thanks

with only GPS it's 20-50 meters wrong or something like 50-100 or 100-200 meters?

Most of the time the error should stay below 50m, but errors around 100m are not uncommon, and even bigger errors are possible.
But the fact that the error is highly unstable and unpredicatble is more significant than the relative error itself. One minute it can show correct altitude, next minute it could show 50m below your real altitude, and next minute 100m above your real altitude. This is probably a drastic example, but definitely possible, even if rare.