Are these sentence correct or incorrect? Correct the verbs that ...

Ira

Are these sentence correct or incorrect? Correct the verbs that are wrong.1. When did he take over the company?2. Where have you been yesterday?3. She has left the company last year.4. They have worked for company for two years.5. We have started flexible working hours six month ago.6. I worked here since last March.7. I've finished my report. Let's go8. What time have you arrived this morning?9. Recent reward schemes have improved staff motivation.