I have fewer free time nowadays
Incorrect - less free time
What's the quicker way to get across your city?
Incorrect - the quickest way
Pizza isn't as nicer as pasta
Incorrect - as nice as
She's the unfriendliest person I've ever met
Incorrect - the most unfriendly
A skateboard is nearly as fast than a bike
Incorrect - as fast as
Women drive more careful than men
Incorrect - more carefully
Driving is more boring than going by train
Correct
Oxford is about the same distance from Cambridge as London
Correct
She's not so tired as she was yesterday
Correct