For your needs, and as you live in Europe, a couple of free-to-use PMR-446 radio is the way to go.
Very cheap, very practical.
https://en.wikipedia.org/wiki/PMR446
PMR-446 devices have only 8 channels, though. You will have to study a little bit about "good manners" in order to share the frequency with some other people who are using it (cranemen, warehousemen, paragliders and hikers, and even local police sometimes).
A decently well-made PMR-446 also has LPD433 capabilities:
https://en.wikipedia.org/wiki/LPD433
For shorter distances LPD433 is much more practical than PMR-446, you have many more channels and much less range, so much less interferences.
If you get so far apart from each other as to make reassembly not an obvious task, you can examine GPS apps for smartphones (such as Real-Time GPS Tracker) which allow you to keep track of your "buddy" (and the buddy to keep track of your position) so that it is easier, when you talk at the radio, to understand the reciprocal position.
Beware that you need a specific radio "ham" license to use frequencies outside of the above mentioned 446 MHz and 433 MHz. The open frequencies should be more than enough to satisfy your needs.
Thank you Diapositivo!
I am afraid I do not understand the technical explanation on the links above, but appreciated! I guess you're right about the open frequencies (and the good manners of course) we're going to use an open frequence (we had already bought two units: 8 Channel Twin Walkie Talkies UHF400-470MHZ 2-Way Radio 3KM Range Interphone Black) we had set the same frequence in both devices - since we do not understand a thing about this, the configuration is what it brings by default - and it seems there're working fine. AFAIK we don't have to have any license, do we? I'll let you know as soon as we have the chance to prove them (in the forest).
As for the GPS apps, I can tell you that it's no possible, not for me but for my friend, although he has a phone is not that "smart" (the phone), but thanks anyway for the suggestion.
Warm regards!