Your English is beautiful just like your snake. No need to apologize for having a second language that isn't as easy as your native language.
I wouldn't survive a second if you put me on a snake board based out of Serbia LOL!
Another feeding option for your boa is quail. I've been using it to get away from some of the fat associated with rats. My male will be 2 years old by the end of June and is about 4 feet 8 or 9 inches. In my opinion he's pretty large and even slowing his growth by feeding less just isn't working. I usually feed every 10-12 days and at certain times it will reach 15-20 if there is a shed involved.
Evenstar has really good feeding advice, and I would suggest finding a copy of THE COMPLETE BOA CONSTRICTOR by Vincent Russo. That book has great info and you will see how seasonal changes, temp drops, increased and decreased light phases all have a role in growth.
Keep the photos and questions coming.