Russian tree? Done!
Fist of all, I have to mention that in Russian you can wish success (singular - успеха) or successes (plural - успехов). It means the same. In English, when you wish success it's always singular (“I wish you successes” sounds weird, correct me if I'm wrong). Okay, now:
“I wish you success in studying Russian language” can be translated as:
“Я желаю тебе успеха (успехов) в изучении русского языка!” (familiar singular “you”)
“Я желаю Вам успеха (успехов) в изучении русского языка!” (formal singular “you”)
“Я желаю вам успеха (успехов) в изучении русского языка!” (familiar plural “you”)
But it is totally fine to drop “Я желаю тебе/Вам/вам” part. It is easier to pronounce cuz it's shorter. Plus, if you aren't sure which form to use, just drop first part and you won't make any mistake! (life-hack by native russian :D). So,
Успехов в изучении русского языка!
I am also a native speaker, and yes, I have found many errors while passing through the course, which is absolutely normal, given the newly acquired beta status :)
Don't feel too bad. I've been here since 2012 and started with French. I was going slow and never conquered the tree, then shifted to German over a year ago. I've been going steady with German ever since and still haven't conquered it yet. The reason for this slowness is that I was a university student juggling several things at once. This English proficiency you are witnessing is an accumulation of twenty years of English exposure everywhere (school and university subjects were all in English too), taking into account that my native language is Arabic. Keep up the great effort, I know you can do it :)
My version: Большое спасибо, товарищ! Может быть, эта форма уже имеется в дереве. Your second sentence, while being perfectly understandable for a Russian ear, sounds not natural. You could say Может быть, что у дерева уже есть эта форма, but better would be Может быть, в дереве уже есть эта форма.
Note there is always a comma coming before "что", used in a meaning of "I think THAT something is ..."