can't view the details on the map

Which map? Is it installed on a device or on your PC for BaseCamp to use?

the map is on my pc for BaseCamp application

Ok, so which map? How did you install it to your PC? Does it appear in the map drop down list in BaseCamp?

so the trails are imported from a backup into BaseCamp app and I can see them on the drop down list in BaseCamp, when I click on one of the trail imported it shows the map with the trail line but i can't see much details like lakes...

Two thoughts:

1. The map detail level is too low.  Its setting is at the far left of the BaseCamp toolbar.  It has options ranging from lowest to highest.

2. Some map display features are turned off.  Their settings are in Edit > Options > Activity Profile > Map Display Features.

Still waiting to hear which map and whether it appears in the BaseCamp map list? You may simply be seeing the BaseCamp base map which has very little detail.

'global map' is it appears in the BaseCamp map list. do I need to download a new one?

The "global" (and "basemap") is a very basic default map. It means you need another map.

BaseCamp will use the map on your GPS device plugged into your computer.

Well that explains the problem.  What device do you have? What map is loaded on that?

You may be able to use Garmin Express to download the map to your PC for BaseCamp to use, but that depends on the map.

The other option is to always connect your device so BaseCamp can read the map from your device.

Alternatively you could copy the map from your device to a removeable drive, either physical or virtual. See here for further details www.javawa.nl/virtualdevice.html