passive voice問題....

both of them are correct~
the main message you would like to bring out in this sentence is that "the shop manager was dimissed".

putting "last weekend" is just an attempt to give more details to the reader, it's less important. The way you put it (in the beginning ie 1st one or at the end ie 2nd one) does not matter.

Also, in passive voice, you don't really have to mention the subject (in this case, ''my father '')who does the act(dimissing the manager). If you do know who is doing the act, ie "my father", then it's better to write it in active voice.

Both of them are correct. The word ' last weekend' can put at the beginning or at the end.