Mine is working too or mine is working also?
Grammatically and semantically, both sentences are correct. The only difference between them is as follows:
1- It's common and natural to use "too" at the end of a sentence, whereas also is not much used so and and is not considered natural if used at the end of the sentence. Also is normally used before a verb, after an auxiliary verb and sometimes at the beginning of a sentence.
2- The use of "also" is a bit formal. On the other hand, the use of "too" is much more natural and common in spoken and informal English.