Hi Andrew In UK English, to 'screw things up' is very informal and I would definitely not use it in an official report. You need to consider other alternatives, like "made a number of errors", "caused some problems", "responsible for mistakes" etc. Exact verb/phrase/tense will very much depend on context.

Hi! 'Screw things up' is an informal saying and would not, in my opinion, be suitable for an official report of any kind. In my experience, I have found that when a report is important, you should keep your language as basic as possible so as not to leave things open to interpretation. It's hard to say what you would substitute the saying for without a context, but if your sentence read 'I believe it would screws things up' then you could try..... result in errors be catastrophic be harmful be damaging be counter-productive

Very informal and some people find it coarse. You could also say "Mess things up", which is also informal, but less coarse.

It can be replaced by other expressions such as 'cause trouble for somebody or something' and 'do something badly or spoil something'.

It's swear. For instance, in the TV shows of the US, people will say 'screw' instead of that F-bomb and never will they say that swear word (not including movies though), you shall never say it, man. However, the word 'screw' does have lots of meanings like 'cheat' and '螺丝' etc etc, so the rest are kinda formal. Even though people will prefer to choose 'cheat' rather than say 'I'm screwed'.