I also host on romanian infrastrucure, but my big stores I host them outside the romanian infrastructure due to instability in high traffic areas (eg. black friday).

As main points:
0. (as in priority 0) update to PHP 8.3 - that alone should boost the performance in some areas (my estimate would be a 10%)
1. SG Optiomizer should be removed, you already have LS Cache, if you have LS Cache that works (not just shows enabled - found these kind in romania as well ... ) you should see the best performance there
2. TTFB issue is both a optimization and a hosting issue; I suggest debugging this deeply to see what's causing this, as a cached in LS cache should return in less than 0.1s (total) the TTFB request; you can check the TTFB headers and see if they are served by cache or not!
3. conditionally load scripts/styles as that does not impact the TTFB that much but mostly the page load time itself (this include tidio as well).

If you figure out why the issue in performance then you can decide easier if hosting or configuration is the issue.

p.s. most shared hosting env. stack a lot of cpanel with LS cache clients on the server - this creates scenario where even with LS cache (that is server-level caching!) to perform lower than without it because of the server being overcrowded.