Germans have a hard time with by
and until
-> Use by
for actions that will be or must be performed at some moment before a time.
-> Use until
for actions that continue and stop at a time.
Examples:
- I work until 17:00. (working happens continuously)
- I will leave by 17:00. (leaving happens once)
- Give me the report by 17:00. (giving the report happens once)
- Fill this out by Friday. (filling it out happens once)
- Jump up and down until I say stop. (jumping happens continuously)
Here is a sort of tricky one:
- You have until Friday to fill it out. ("having" is a state with continues until Friday).