Are these sentences correct:
1-This key to open the gate is a bit difficult to use but the other one is fine.
2-This key for opening the gate is a bit difficult to use but the other one is fine.
3-This way to repair the car is better than the other one.
4-This way for repairing the car is better than the other one.
(In the first case, I'd use "this key to the gate" and in the second "this way of repairing the car", but I want to see if the structures of the other sentences are correct, even though the sentences might not be very common.)
In 2, I'd say 'the key for the gate' and omit 'opening, but I wouldn't say it's wrong, just a bit iffy.
3 is fine, but I don't like 4- I'd use 'of'.