麻烦英语高手帮我修改一下这句话的语法,可以的话意思不变的情况下修改这句话的结构,However,the date I been there was mid-February and then I found out the earliest dog living there was came in by mid-January.I guess it might not be a long time for dogs to stay.我去的日子大约是2月中旬,我发现再那里呆的时间最长的狗狗也只有一月中旬,所以我猜想可能狗狗并不能在这里待很长的时间意思是说，我去的时候是2月中旬，在那里呆的时间最长的狗狗被送来的时间是一月中旬

The day i got there was in mid-Feruary,and soon i noticed that the earlist dog living there had arrived only around mid-January. So i won't suppose any dog may keep there long.
建议楼主用英语式的思维方式。而不是简单汉译英。只是建议，说错勿怪哈。希望能帮到您，祝进步！

However, the date when I got there was mid-February and then I found out the earliest dog living there was brought in mid-January. I guessed it might be too long for the dogs to stay there.
然而，我到那里的时候是二月中旬，那时我才知道最先到那里生活的狗狗是在一月中旬带来的（bring 的被动式），我想狗狗在那里待的时间可能太长了，无法再待下去了。（too...to...，太...以致不能...）

However, the date I arrived there was mid-February and then I found the dog with longest stay there came in mid-January. I guessed it might not be a long time for dogs to stay.

这话没错，翻译也没错；就是最好把话说漂亮点就行

I went there in about mid-February and found out that the dog that stayed there the longest was only one month.So I thought the dog(s) could not stay there for a long time.