я достал в кармане для ключей, чтобы поискать ключ инженера для доступ на запретный этаж сверх, и свой аппарат.
'я достал из кармана ключи, чтобы искать А и Б'

Is this partly due to the comma after 'сверх'?
If it was written without a comma after сверх (which should be наверху anyway) would it be slightly more intelligible?
'я достал в кармане для ключей, чтобы поискать ключ инженера для доступ на запретный этаж наверху и свой аппарат.'
Its still a clumsy sentence though, if I was going to write it again I'd start from scratch.


Лифт [дополз] до шестого этажа:- It does say roughly what I wanted it to, but I wanted to emphasise the idea of it juddering as it stopped. I think I shouldnt have put a comma after my 'этаже' either...

полез в карман:- is this an idiomatic use of полезть?

чтобы достать универсальный ключ:- makes more sense than mine.

попасть:- yes, a less clumsy way to say it.

лифтовая надстройка:- I looked on wikipedia.ru to get 'помещения машинного лифт', лифтовая надстройка sounds more like something someone would actually say!

наверху:- For some reason I cant seem to remember that this is (effectively) locative, and has 'у' on the end like 'саду', etc (different part of speech, of course.)

звук:- is there a way for me to know when to use звук, and when to use 'шум'?

Я не обратил на это внимания:- apparently needed more information than we would use here in English.

нашаривать/нашарить:- That makes sense, but:-

'... я охнула и стала шарить вокруг себя в поисках меча.'
'I gasped and started to fumble around myself in search of my sword'

(from https://www.lingvolive.com/en-us/translate/ru-en/шарить; like wikivox.ru, but with translations beside each sentence; but unlike wikivox, you have to be specific about which form of a word you search for.)

It seems one can 'шарить в поисках' something, although нашарить is simpler, if I can remember it.

This explains 'for' in Russian succinctly, although for some reason, it's not sinking in for me.
Saying 'for' in Russian

What I really need to do, I think, is to sit and look at all this, and get an idea of what things I don't use properly, and prioritise learning those. Not sure how yet.