fit
- suit
‘fit’
If clothes fit you, they are the right size, neither too big nor too small.
That dress fits you perfectly.
He was wearing pyjamas which did not fit him.
In British English, the past tense form of fit is fitted. In American English, the past tense form is fit.
The boots fitted him snugly.
The pants fit him well and were very comfortable.
‘suit’
If clothes make you look attractive, don't say that they ‘fit’ you. You say that they suit you.
You look great in that dress, it really suits you.