Would you still take the job even though a different salary was originally agreed upon?

Briefly about me: I am an economics student in my 3rd bachelor's year from Germany.

I need your advice, I was approached for an internship position at a law firm for their business/finance department. I am currently still working as a student trainee (20h per week) in a startup. At the interview a salary of 2.5k€ per month was originally agreed, alternatively a salary of 2k€ + profit sharing on projects was an alternative. In further conversation I was told that the profit sharing was probably not possible after all, as I will only be working there full time for 6 months for now. And are now back to the original 2.5k. Now I got a call today that the firm will hire 2 more lawyers and the financial capacity supposedly does not allow me to pay the verbally agreed 2.5k. I was now offered 1k for a part time position (20h), but I really wanted to work full time.

My question to you: should I accept the part time offer or tell him that I want to stay with a full time position and for that I would go down from 2.5k to 1.6k. Or should I accept or offer anything at all? I'm really pissed that it has come to this. Especially since I've been waiting for almost 3 weeks for the employment contract to be sent to me and today I got this call... How would you act in my position?

Thank you in advance!