Learn Polish: Chcę, żebyśmy negocjowali nowe ustępstwa. - I want us to negotiate new concessions.

Żebyśmy combines the conjunction żeby (so that) with the personal ending -śmy (we). When expressing "I want us to do something", Polish literally says "I want so that we did something". The ending for "we" detaches from the verb and attaches directly to żeby.

Why is negocjowali in the past tense form if this is about a present or future desire?

After żeby (and gdyby), you must use the past tense form of the verb, regardless of when the action happens. The full verb form for "we negotiated" is negocjowaliśmy, but because the -śmy ending moved onto żeby, we are left with just the third-person past base negocjowali.

Can I leave the ending on the verb and say żeby negocjowaliśmy?

No. While personal endings in the regular past tense can sometimes float around the sentence, words like żeby and gdyby act like strong magnets. They force the personal ending to attach to them, making żeby negocjowaliśmy grammatically incorrect.

What case is nowe ustępstwa and what is its singular form?