OK what the actual fuck is going on within this company.

TL;DR: Spaghetti Copy/Pasted code that made me mad because it's just a mess

I just looked into a code file to search for a specific procedure regarding the creation of invoices.
I thought "Oh this is gonna be a quick look-through of like 1000 lines MAX" turns out this script is 11317 fucking lines long and most of it's logic is written there multiple (up to 6-7 times). And I'm not talking about a simple 10 lines or something. No! Logic of over 300 lines.. copy & pasted over .. and over .. and over?! I mean what the fuck did this guy drink when he wrote this.

Alsooo 10000 of those 11317 lines is ONE FUNCTION.. I kid you not! It's just a gigantic if / else if construct that, as I said before, contains copy-pasted code all over the place.
Sadly my TL thinks that code cleanup / optimization is "not necessary as long as it works" like wtf dude. If anyone wants to ever fix something in this mess or add a new feature they take a few hours longer just to "adjust" to this fucking shit.
This is a nightmare. The worst part: This is not the only script that has shit like this. We got over 150 "modules" (Yeah, we ATTEMPTED something OOP-ish but failed miserably) that sometimes have over 15000 lines which could be easily cut down to 1/3 and/or splitted into multiple files.
Let's not start about centralization of methods or encoding handling or coding standards or work code review or .. you get the point because there's a character limit for one rant and I guess I'd overshoot that by a lot if I'd start with that. Holy shit I can't wait until my internship is over and I can leave this code-hell!!