What is the mistake: I work here since two years.

[Sonnete]

I have seen him yesterday..

I work here since two years..

[Yankee]

Hi Sonnete

You should try first.
What do you think is wrong with those two sentences?
.

[Daemon99]

[Edison_Chen_e_c]

1. I have seen him yesterday.

Though "have seen" can be a kind of past tense yet in the sentence it has a definitely time point there "yesterday" so that you need past tense.

Correct: I saw him yesterday.

cf:

I can't go with you because I broke my leg. (wrong)
I can't go with you because I have broken my leg. (correct)

Are you finished? Yes, I just have finished the letter. (correct)
Are you finished? Yes, I just have finished the letter several hours ago. (wrong)
Are you finished? Yes, I just finished the letter several hours ago. (correct)

2. I work here since two years. (wrong)

Correct:
I have worked here since 2005.
I have worked here since I graduated.
I have worked here for two years.