in my opinion, to have all this improve is more on the server side ... it does not have the header and expires module that allows you to put expiration time ... (Cache-Control) ... the images compress, you I recommend https://tinypng.com/ there is a module for prestashop ... an important detail with prestashop and you have not done it in back-office -> Advanced Parameters ->Performance active cache and the 3 CCC (Combine, Compress and Cache)
I await your comments