You can’t change timestamps on your trophies once earned. Timestamps are logged on the psn servers and synced to your account from the server-side clock.
If you’re planning on using saves from this site - or any other site with save files, I would recommend playing games legitimately first. Unlock as many trophies naturally. Then start looking at the requirements of other trophies. Plan ahead what you want to unlock with the saves - read the forum thread & instructions of posts carefully. Look at youtube guides etc. If you have a second psn account you aren’t worried about - test saves to see what unlocks. But Keep in mind that you can’t change the timestamp on a trophy once unlocked so plan accordingly.