Set a limit and negotiate a workable alternative
Ich helfe dir gern, allerdings kann ich nur bis sechs bleiben.
Decline part of a request politely while stating availability and offering a feasible option.
A respectful boundary can be clear and friendly at the same time. Ich helfe dir gern, allerdings kann ich nur bis sechs bleiben states both willingness and a limit. Allerdings links a contrasting main clause, so its finite verb follows immediately. Dagegen contrasts alternatives: Am Freitag kann ich nicht; am Samstag dagegen habe ich Zeit. You do not need to invent an excuse. If you offer an alternative, ensure it fits the time and resources already mentioned. A compromise is agreed only when the other person accepts it; silence or a new proposal is not acceptance.
Ich helfe dir gern, allerdings kann ich nur bis sechs bleiben.
I am happy to help you, but I can only stay until six.
Am Freitag kann ich leider nicht; am Samstag dagegen habe ich Zeit.
Unfortunately I cannot on Friday; on Saturday, however, I have time.
Mehr kann ich im Moment nicht übernehmen.
I cannot take on any more at the moment.
Könnten wir zuerst die schweren Kisten tragen?
Could we carry the heavy boxes first?
Danach müsste jemand anderes die Möbel abholen.
After that, someone else would need to collect the furniture.
Dann halten wir fest, dass ich von vier bis sechs helfe.
Then let us agree that I will help from four until six.
A respectful boundary can be clear and friendly at the same time. Ich helfe dir gern, allerdings kann ich nur bis sechs bleiben states both willingness and a limit. Allerdings links a contrasting main clause, so its finite verb follows immediately. Dagegen contrasts alternatives: Am Freitag kann ich nicht; am Samstag dagegen habe ich Zeit. You do not need to invent an excuse. If you offer an alternative, ensure it fits the time and resources already mentioned. A compromise is agreed only when the other person accepts it; silence or a new proposal is not acceptance.
Decline part of a request politely while stating availability and offering a feasible option.
Do not write allerdings ich kann nur bis sechs bleiben. Do not offer two hours of help when only one hour is available.
Willingness or polite refusal + clear limit + feasible alternative + confirmation. Allerdings + finite verb + subject.
Write a 100–120-word exchange about helping someone move. State a time limit, explain a practical constraint, offer an alternative and confirm the agreed tasks and time.