给出一篇英语写作，对其中的语法错误进行纠正，并解释为什么这些错误需要纠正。
There are some grammar errors in the following paragraph:

I feel more better today than yesterday. Me and my friend seen a movie last night. It was a action movie with lots of explosions. I could of sworn I seen the main actor in a different film before. Anyways, the movie was so good that me and her wants to see it again.
I feel better today than I did yesterday. My friend and I saw a movie last night. It was an action movie with lots of explosions. I could have sworn I had seen the main actor in a different film before. Anyways, the movie was so good that my friend and I want to see it again.

Explanation:

1. "More better" is incorrect as "better" is already comparative. 
2. "Me and my friend" should be "My friend and I" as the subject should come before the verb.
3. "Seen" should be "saw", as it's in the past tense and "seen" is used with "have" or "had".
4. "I could of sworn" should be "I could have sworn" for proper grammar.
5. "Wants" should be "want" as it should agree with the subject, "my friend and I." 

These errors need to be corrected because proper grammar is necessary for clear and effective communication. Using correct grammar ensures that the message is conveyed accurately, reducing the chance of misinterpretation. Additionally, using proper grammar helps to establish credibility and professionalism in written communication.