can anyone check my grammar please?

The main problems Arnold Schwarzenegger must focus on are the immigration issues, college tuition costs and high unemployment.

Looks good -- if you put a comma after costs.

okay. thank you ms. Sue!

Sure! I'd be happy to check your grammar. Here is your revised sentence:

The main problems on which Arnold Schwarzenegger must focus are immigration issues, college tuition costs, and high unemployment.

The changes made include:

1. Removing "The" before "Arnold Schwarzenegger" as it is not required.
2. Adding "on" after "problems" to clarify the relationship between Schwarzenegger and the issues.
3. Adding commas between "immigration issues," "college tuition costs," and "high unemployment" to separate the list items.

Remember, it's always a good idea to proofread your work and use correct punctuation and grammar. Additionally, having someone else review your writing can help you catch any mistakes you might have missed.