Contract for electrical installation

Hello everyone,
A few general questions about the electrical installation trade:
Do you need a contract for the electrical installation before work begins, or is acceptance of the offer enough? If yes, who prepares the contract? Is there documentation by the electrician during the construction phase where the individual progress/milestones are recorded?
Who approves the work at the end or does he also give us the warranty if something does not work after completion?
Sorry for the many questions. I have zero experience with this. I will probably have to make a decision on the offers within the next two weeks...
Thanks in advance for your help!!

Do you need a contract before starting electrical installation work, or is acceptance of the offer sufficient?

What else would you want to regulate additionally in a contract? Accept the offer and maybe agree on the execution period. That is usually sufficient.

Who approves the work in the end?

The client = you or your site manager, whom you pay for that.

Does he also give us a warranty if something doesn't work after completion?

The electrician can't avoid that. But that is normal as well.

What else would you like to regulate in a contract? Accept the offer and maybe agree on the execution period. That is usually sufficient. The client = you or your site manager, whom you pay for that. The electrician can't avoid that. But that is normal.

Thank you for the quick response! I understood from you that an offer plus a period agreement is sufficient. That works for me too. I thought a contract was needed where the warranty, down payments, and such are regulated. In terms of technical acceptance, I definitely cannot as a layperson. At most, I see if, for example, the number of sockets is correct, if at all.

Don't forget that you generally need the electrician right at the beginning of your construction for the [Fundamenterder].