Latitude Festival

因为我跟我的朋友们一起在夏天七月份会去一个音乐节叫Latitude，所以我很开心。

It is an activity in the future so you need 会 before the verb.

Because you are telling a festival for the first time, so adding 一个 is more natural. It is the same rule like English. 

因为我们从不没去过音乐节，所以我也有点儿紧张。

不 is only used in current tense and future tense. 没 is used in past tense.

 所以 always need a comma ahead.

Latitude在suffolk。我们会去在Latitude去露营四天。我也不没去露营过！

我必须买很多的东西，一瓶水，帽子，防晒霜， 还有更很多其他的东西！

因为最近我病了很多久，所以我需要有一些乐趣。我很兴奋！

I think 'ill a lot' means you have been ill for a long time. 病了很多 may be taken as 'having different kinds of sicknesses'. 

'Have some fun' can be translated into 找点乐子.

需要有一些乐趣 is awkward. 

Latitude Festival

（因为）今年夏天七月份我要跟我的朋友们一起夏天七月去一个叫Latitude的音乐节叫Latitude，（所以）我很开心。（因为）我们从不没有去过音乐节（所以）因此我也有点儿紧张。
Latitude在suffolk。我们将在Latitude去露营四天。我也不去曾露营过！我必须需要买很多的东西，：一瓶水，帽子，防晒霜， 还有更多的东西！（因为）最近我病了很多，所以我需要有一些乐趣。我很兴奋！

This summer in July I am going with my friends to a music festival called Latitude, so I am very happy! We have never been to a festival before so I am also a little bit nervous. latitude is in Suffolk. We will be camping at Latitude for four days, I have also never been camping before! I have a lot to buy; bottles of water, a hat, sunscreen, and more! I have been ill a lot recently, so I need to have some fun. I am very excited!

Latitude Festival

因为我跟我的朋友们（"们"字可省略）一起

夏天七月去音乐节叫Latitude所以我很开心。(在七月的夏天去Latitude音乐节所以我很开心。     会更通顺  )

因为我们从不去过音乐节所以我也有点儿紧张（"兴奋"是不是比较贴切?）。
Latitude在suffolk。我们在Latitude去露营四天。

我也不曾去露营过！我必须买很多的东西，一瓶水，帽子，防晒霜， 还有更多的东西！

因为最近我病了很多，

所以我需要有一些乐趣。（我们常会说"我需要找些乐子"）

我很兴奋！

This summer in July I am going with my friends to a music festival called Latitude, so I am very happy! We have never been to a festival before so I am also a little bit nervous. latitude is in Suffolk. We will be camping at Latitude for four days, I have also never been camping before! I have a lot to buy; bottles of water, a hat, sunscreen, and more! I have been ill a lot recently, so I need to have some fun. I am very excited!

Latitude Festival

因为我跟我的朋友们一起夏天七月去音乐节叫Latitude所以我很开心 (这个7月份的夏天我和我的朋友们要去Latitude音乐会,我非常的开心.  )。因为我们从不去过 (从来没有去过) 音乐节所以我也有点儿紧张。
Latitude在suffolk。我们在 (会在=will be) Latitude去露营四天。我也不去 （从来没有=never been）露营过！我必须买多 (很多=a lot)的东西，一瓶水，帽子，防晒霜， 还有更多的东西！因为 (但是=but，因为=because）最近我病了很多 (我最近生病了 - 主语 我 放在前面然后才叙述我怎么了)，所以我需要有一些乐趣。我很兴奋！

This summer in July I am going with my friends to a music festival called Latitude, so I am very happy! We have never been to a festival before so I am also a little bit nervous. latitude is in Suffolk. We will be camping at Latitude for four days, I have also never been camping before! I have a lot to buy; bottles of water, a hat, sunscreen, and more! I have been ill a lot recently, so I need to have some fun. I am very excited!