By & Until

Germlish = We have to finish the project until Friday.

by + a time means "no/not later than" Tip: think deadline (die Frist)
e. g. The ABC project has to be finished by (no later than) Dec. 15.

until + a time means “up to a time”

You cannot use until with this meaning.
NOT The report has to be finished until 3 o'clock.

Something continues until a time in the future.
e. g. Many grocery stores stay open until 8 pm. = I can go shopping up to 8 p.m.

What you want to say: We have to finish the project by Friday.