Welcome back to the Wefugees Community and thank you for reaching out to us again.
Unfortunately, I can not share any experience regarding the process of verifying documents in Gambia (do you mean the so-called "Legalisation"). I tried to make some research and found this brochure, published by the refugee council in Baden-Württemberg. On page 13 they write that the legalisation by the Gambian Foreign Ministry is supposed to be a non-complicated procedure. You didn't explain what type of documents you need to "verify", the brochure is however giving broad information on different topics (it is in German though).
The above mentioned refugee council and also the "Arbeitskreis Asyl in Donaueschingen" seem to be really experienced with similar situations. Maybe you can contact them as well for further information.
I hope this helps and please don't hesitate to get back to us also.
All the best,