I know several people who have started learning an instrument as adults. The successful ones all had teachers at least occasionally when they started out. The successful ones also all liked playing and did so quite a bit between lessons. If you call it "practice" it somehow seems harder to do it, but if you are just playing the instrument that you do in fact want to learn how to play, then you are likely to do it more. The more playing, the more success. Hope everyone around you likes lots of banjo, because they will be hearing a lot of it.
Also, after only a few weeks, you will know enough to play along (as a junior participant) in jams. Strongly encourage you to see if there are any beginner jams in your area. It connects you to other players and really helps get you jump started into adequate playing. Good community too. Be prepared for Banjo player jokes (all meant well, I'm sure).