[Grammar] a friend of mine celebrated his birthday last Saturday evening.

[sania-baharat]

Are these two sentences OK?

I’m going to talk about the service we received in a restaurant where a friend of mine celebrated his birthday last Saturday evening.


I’m going to talk about the service we received in a restaurant which a friend of mine celebrated his birthday last Saturday evening in.

 

[Matthew Wai]

I’m going to talk about the service we received at the restaurant where/at which a friend of mine celebrated his birthday last Saturday evening.

 

[sania-baharat]

Thanks.
We say "at a restaurant" not "in a restayrant".
I’m going to talk about the service we received in a restaurant that a friend of mine celebrated his birthday last Saturday evening at.

 

[Tarheel]

Use Matthew's suggestion (with "where").

 

[Tdol]

I’m going to talk about the service we received in a restaurant that a friend of mine celebrated his birthday last Saturday evening at.

At gets a bit lost here. I would move it to after his birthday.