I came to a park cuzbecause it’s sunny and I felt like going out.

It’s a bit cold outside because of the high wind but felt notit did not feel so bad.

I bought a travel guide book forabout star watching ands I am planning to go camping this summer for it.

I came to a park cuz it’s sunny and I felt like going out.

It’s a bit cold outside because of highthe strong wind but it felt not so bad.

I bought a travel guide book for star watching and am planning to go camping this summer for it.

I came to a park cuz it’s sunny and I felt like going out.

*It's ok to use "cuz" if you want to speak slang.

It’s a bit cold outside because of the high wind but felt noit didn't felt so bad.

I bought a travel guide book for star watchgazing and am planning to go camping this summer for it.

* better use "star gazing"
* It's ok to use "this summer for it". (If you mean you want to go camping to do star gazing). People will understand it.

I came to a park cuzbecause it’s sunny and I felt like going out.

Need to add a second 'I' to indicate you are talking about yourself, as you've had 'it' as a pronoun between this statement abound yourself and the first statement about yourself.

It’s a bit cold outside because of a high wind but feltdidn't feel not so bad.

High wind is singular so would use the indefinite article in front of it; alternatively you could say 'high winds': plural. Negative form of felt is "didn't feel". Simple present and past forms of verbs in English you 'do' as an auxiliary.

I bought a travel guide book for star watchgazing and am planning to go camping this summer forwith it.

The word is normally 'stargazing'. I am not sure what you are trying to say with 'am planning to go camping this summer for it'. If you are talking about the book then it would be 'with it' to indicate you are taking the book along. If you are wanting to say, you are going camping to order to stargaze then I would say.
'I bought a travel guide book for stargazing and am planning to go camping this summer in order to do this.'

I did not know you could buy travel guide book for stargazing but apparently you can. :)