I need help with my thumbs "there long" not falling between the keys with it nail or hitting 2 notes because bent. 
I have done my scales slow and work my way up to about 100 in few minutes. So I know them I've also played Bach invention 1. 
People tell me I just need keep practicing but I sit for hrs practicing straight into Fur Elise than my compositions. 
And some times my hands are ice cold or very very slippery on the keys "digital piano" and this all frustrates me and I'm not getting much help.
 
Thanks

Technique may be a problem. Just practicing may not be enough. If we practice our mistakes, we keep our mistakes. A good piano teacher might be able to give you some useful advice there. As far as your hands being cold, that sounds like a medical issue that you should have a doctor look at. I have type 2 diabetes and my hands get cold very easily. If I hadn't seen a doctor about that I never would have known what the problem was. 

One thing my piano teacher emphasized was that I needed to play on my finger tips. I would be lazy and play with my hands level with the keys. She made me focus on having my hands above the keys over them.... like "walking a spider" with your fingers. That prevents the thumb from easily pressing 2 keys at the same time. BTW: She was a small lady with short stubby fingers and she managed to play some amazing things. As a young (early teen) my finger span was actually longer than hers.
 
She also tried to teach me to feel the music as I played it with fingerboard technique that resembled rolling waves..... hard to explain with words..... but after all these years, I finally "get it".

Same thing my teacher says I take everything slow and speed up tempo by tempo. Oh dang that stinks sorry. I have cp in my wrist.
 
That problem think my teacher shorter so what works for him may not for me. My feet 10 inchs long lol
What this fingerboard? that help you feel the music I feel the music but don't mind trying some than new that could help.
 
Thanks