I would suspect this has to do with timezone data. In the live caches Cachly gets the timezone from the API for all caches and it knows how to correctly convert the timestamp. If you import a GPX, there likely is no timezone data and Cachly just uses UTC.
The navigation provider can be chosen in settings, and you can choose Apple. Google, Waze or TomTom. Once you do that, tapping "Navigate" will use that mapping app.
Is that what you were asking?
Geocaching HQ has placed some limits on trackable visits. Please see: https://help.cachly.com/article/130-trackable-visit-limits
I limitation affects Cachly and all other Geocaching partners and apps. Please also make sure you are on the newest version of Cachly.
The GPX format exported from Google Earth is likely different from what Cachly is expecting. We use specific fields and attributes that follow the geocaching.com format. I am not sure how GE does it.