(Rewriting sentences in the past tense by changing the ADVERB--TIME INDICATOR and the necessary ASPECT MARKER)
This is my work, anyone please feel free to correct!
6）ngo5 sai3lou2 soeng6go3yut6 maai5 zo2 ce1.
我細佬上個月買左車。
7）ngo5dei6 soeng6go3lai5baai3luk6 hoei3 zo2 waat6syut3.
我地上個禮拜六去左滑雪。
8）koei5 yi5cin4 lai4 zo2 gno5 uk1kei2 taam3 ngo5.
佢以前嚟左我屋企探我。
(nerd bonus: present tense)
koei5 yi4ga1 lai4 ngo5 uk1kei2 taam3 gno5.
佢而家嚟我屋企探我。
koei5 lai4 gan2 ngo5 uk1kei2 taam3 ngo5.
佢嚟緊我屋企探我。
9）ngo5 a3go1 yi5cin4 hai6 lou5si1.
我阿哥以前係老師。
10）ngo5 go3mui2 soeng6go3gau2yut6 hoei3 zo2 faat3gwok3.
我個妹上個九月去左法國。
11）nei5 tung4 uk1kei2yan4 cam4maan5 hoei3 zo2 sik6 soeng6hoi2 coi3.
你同屋企人尋晚去左食上海菜。
12）keoi5dei6 soeng6go3lai5baai3 bun1uk.
佢地上個禮拜搬屋。
13）ngo5 ting1ziu1 zo2 sap6yat1dim2 soeng5 gwong2dung1wa2 tong4.
我聽朝左十一點上廣東話堂。
Well done!
Only for last September, we would normally say soeng6 nin2 gau2 yut6 上年九月 (last year September)
And I would like to know why you didn't add zo2 for question no. 12? It's not wrong, that's why I want to know the reasoning of your choice.
When we started the exercise together, I had noted (and underlined!) that zo2 左 is used for a one time action, and also that I had used it for questions 3 (living in Vancouver) and 4 (must go to work) and then crossed it out when corrected in class. So I guessed that I could omit it for questions 9 and 12, especially since it goes after the verb and I wouldn't have been sure where to place it without it being awkward ≧ ͜ ≦
So, I'd say both are correct for no. 12. When you put zo2, the moving is being emphasized. If you omit it, it's being used more like «imparfait» in French, we would expect some more details coming after that sentence.