password protecting

i was wondering. if there was a way to password protect my macbook in like so youll need passoword before deleting anything

and if i could make you need password before downloading stuff.

i know i can use password for installing but i hate when i let other 1 person use my laptop and i got like 5 things downloaded on my macbook -.-

basically: password protect before download and for deleting things?

Simply do not allow anyone to use your computer while logged in to your account.

Preferably, don't allow anyone to use your computer at all.

But, if you must, let them use the Guest account or create another non-admin account for them to use.