I have been writing one more journal oing in my notebook everyday for more than 50 days. I have been journaling in my notebook everyday for more than 50 days.

I have been writing one morea journal oin my notebook for more than 50 days. I have been writing a journal in my notebook for more than 50 days.

Now that I try toam write iting in English, it helps my more often, I am able to thinkings straight into English the language. Now that I am writing in English more often, I am able to think straight in the language.

You could also say "Journaling in English daily has helped me think directly in the English Language."

Now that I tryI am trying to write it in English, it helps mye thinkings straight into English. Now I am trying to write in English, it helps me think in English.

Adding "straight into" isn't really necessary here.

Today, I fiound out that I need to buy another onenotebook/journal. Today I found out that I need to buy another notebook/journal.

You could also say "Today I realized that I need to buy a new notebook/journal." It is better to restate that 'another one' is referring to the notebook since the previous sentence was about a different subject.

Today, I fiound out that I need to buy another one. Today, I found out that I need to buy another one.

It would be better to say "I realised that...."

Because the notebook has onlyit only has 60 days' worth of paper. Because it only has 60 days' worth of paper.

Since I edited the previous sentence to include 'notebook', in this sentence we can refer to the notebook as 'it'.

I want to use this brand's notebookbuy from this notebook's brand again, because I am already get used to it. I want to buy from this notebook's brand again, because I am already used to it.

You original sentence could also be correct with a minor fix like so: "I want to use this brand's notebook again, because I got used to it".

I want to use this brand's notebookbuy a notebook from this brand again, because I have already geot used to it. I want to buy a notebook from this brand again because I have already got used to it.

On the other hand, I also want to use otherwould also like to try new brands whichthat I haven't used before. On the other hand, I would also like to try new brands that I haven't used before.

Check out an explanation on using that vs. which. To be honest, this topic can be pretty confusing, so don't focus too much on it. When editing this sentence, I did not think about the grammar rules, but rather what I felt was more natural.

On the other hand, I also want to usetry other brands which I haven't used. On the other hand, I also want to try other brands which I haven't used.

Since you have not used them yet, you would use "try"

For this reason, I have browsed on the many internet shops, but I do not still decide astill haven't yet decided on the next notebook. For this reason, I have browsed many internet shops, but I still haven't yet decided on the next notebook.

For this reason, I have browsed on the many internet shopmany websites, but I do notam still not decide a next notebookd on which notebook to get next. For this reason, I have browsed many websites, but I am still not decided on which notebook to get next.

I should think about it again tomorrow again. I should think about it again tomorrow.

I think your original sentence can be correct, however I edited it in the way that sounds more natural.

I shouldwill think about it again tomorrow again. I will think about it again tomorrow.

It's more natural to say "I will.." as you are (most likely) going to do it