Just to add from my guitar teaching days.....
ALWAYS practise “slow and right” keeping everything at a consistent speed, which effectively means playing EVERYTHING as slow as the most difficult bit
Practice doesn’t make “perfect” - practice makes “permanent”
So if you play a piece and play the easy bits fast and the hard bits slow, or you don’t play correctly as you are trying to go to fast, you will end up embedding this - making it harder to unlearn later
This was THE most common barrier to effective learning - especially for younger boys who wanted to rush ahead
Anyone can play fast and wrong!