【【【【【这句话能这样写吗？】】】

可以 ,但有点错误

Could you guess what I did a few days ago?

或者Could you guess what I did recently?

past time范围太广了

可以

不能 太汉语了
Guess what I did in the past time?

can you guess ,what i did a few days ago

语法有问题

应该是：

Can you guess, what did I do a few days ago?

语法上没什么错误，但因为是过去时，用could比较好
如下：
Could you guess what i did a few days ago?