Cheers all, I'm a PHP developer working on an existing PrestaShop site trying to deal with the override mechanism, I'm a PS newbie but I read the documentation.
A big thank you to those who will read and reply to my following questions. The site (v1.6.x) uses a template where I'm asked to change small details such "move this 10px to the left" or "add a input field below this image". Most of these questions come from failed attempts to simple edit which didn't reflect in the public site (even after rebuilding PS cache).
Q1: Most of the things I have to change come from the theme itself or some core page (one is in the main root, not even in the classes/controllers folders). I read several threads on this forum suggesting to clone the theme and "hard-code" changes on the cloned theme, but does the theme update itself as happens for modules and so I lose the changes every now and then?
Q2: When overriding a class/controller/module, I assumed if I need to change things only in (example) the PHP file I do not need to prepare/upload eventual tpl/css/whatever that the original module/controller/etc had, right? I create only what I need to change right?
Q3: overriding a php file basically asks me to extend the class that the original .php file constitutes, eg. a file called "randomclass.php" is considered the "randomClassCore" class and in my override file I'll set up my "randomClass" to extend said "randomClassCore" class, did I get this right?
Q4: php files are overridden as classes extension, but what about .tpl and .css files? Should I just clone what is in the original file and edit/add/remove what I need? I did this for a .tpl within the template but it didn't work. One file I worked on was located in root\themes\theme_name\shopping-cart.tpl and I put the override in root\themes\theme_name\override\shopping-cart.tpl, rebuilt cache, and no change happened so I assume it's the wrong folder?
Q5: about translations, when in the .tpl file I find things such "{l s='ok'}", there is a way for me to conveniently detect in the admin page which field is the one that provides that translation? (there are A LOT of lines!)
A huge thank you to those that will invest their time explaining me or giving me hints about my problems/doubts, have a great day!