Is this sentence correct?

"I have to practice to prevent in order not to forgetting the words that I've learnt.ed"

There are many other ways of saying the same thing, eg:

"I have to keep on practising so as not to forget words that I [had] learnt."

Is this sentence correct?
Thanks ahead

It's correct but doesn't sound natural. I would say:

I have to keep practising to prevent myself from forgetting the words that I've learnt.