ALIMENTATIO AD EXERCISES

HELLO EVERYONE I'M NEW HERE
THR TOPIC'S NAME IS ALIMENTATION AND EXERCISES BUT I'VE POSTED IT IN "FITNESS AND EXERCISE"....SORRY IF I'VE PUT IT IN THE WRONG PLACE

i'm writing you because i have some questions for you:

i have been lifting weights for one week and i've decided to pay a personal trainer to correct my exercises forms.
he said to me that there is the risk that my legs (where is concentrated my body fat) will be more bigger because the muscles will be bigger but the fat will stays on.

Is that true ??

Now i know tha i have to motivate myself but when someone says to you somethink like that i think it's normal be a little demoralized.

Will lifting ghisa make my legs bigger ??
if i increase my lean body how can fat stays on ??

Thank you very much for your reply i need motication and answers