I hope "mental outpourings" transfer as well as I want into the English language.

I like "mental outpourings", but it sounds self-deprecatory to me as if you didn't value what your wrote. "Mental", "being mental", "going mental" are slang expressions for "crazy", "being crazy", "getting upset or angry", so someone may apply a negative meaning to the word "mental". "Outpourings" suggests a quick secession. If this is what you wanted to express, kudos! Otherwise, something neutral may be better.

mMental oOutpourings

It's good to capitalise the main words in a title, but not words like 'an' 'the' 'of' 'to' etc.

Yesterday, I did manymade a few/a lot of mistakes when I tried to use the past tense.

In order to get rid offix this problem, I've spent some time recently with my grammar book.

The topics I have seenrevised were on the distinction of the present perfect and the past simple.

I guess as it's only one grammar point you are mentioning you would write something like:

I revised the distinction between the present perfect and the past simple tenses.

While I always thought I amwas able to choose the correct tense when I write something in English, I was surprised by how many different rules you have to keep in mind.

Some of them are pretty hard to differentiate between as well.

Some of them are pretty hard to tell apart, as they are so similar.

For instance, on the one hand, you have to use the simple past when you are interested in when a present situation began,. (can I begin a new sentence with "on the other hand"? )oIn the other handsituations, you have to use the present perfect tense when you talk about how long an existing situation has lasted.

For instance, on the one hand, - i would use either one or the other, not both.
Using on the one/other hand is for comparisons or balancing arguments, as opposed to listing two different grammar points, and doesn't quite work here.

To show you what I mean I will try to apply these rules in the following sentences.

When did you start doing your own music?

doing music works but is quite casual.
making music. writing your own music.

I have donedid my homework over a long period of time.

Not sure if it's present perfect but I would write it like this.

My grandparents haven't left their house over the past 2 weeks, yet they are cheerful about it.

My grandparents haven't left the house in two weeks, and they are cheerful about it.

I feel like I was'm in school again.

It feels like I'm in school again.

However, later I will visit my grandparents later.

However is used to contradict something you previously said, and doesn't quite work here.

I'm planning on visiting my grandparents later.

In case, you might bf you are wondering whether or not it's true that they haven't left their home in the last 2 weeks, - it's not.

RegardingAs for my visit later on, I have no specific plan in mind.

'I have no set plans.'
'My plans aren't set in stone'
'I'm going to take it as it comes'

We are probably going to stay inside because of the bad weather.

We'll probably stay inside because of the bad weather.

After checking on my grandparents, I wi'll visit some friends who are playing some board games this evening.

You would write it as' After checking on my grandparents, I'm planning on visiting some friends
or 'I plan to visit some friends'
as you are talking about your 'plans for the evening'.

It won't doubt it will be very exciting, but I am excite'm glad to have been invited to a calm evening with my friend's brother'squiet night in with my friends.

It's a bit of a contradiction saying it won't be exciting but you are excited. Friend's brother's friends is a mouthful. If friends of your friends brothers friends are your friends then just call them friends!

A few seconds ago I came up with the idea to start a new sentence with the word "but".

haha.
Begin/start a sentence, instead of start a 'new' sentence, works a bit better. Every sentence you begin is a new one so you wouldn't have to mention it.

I am happy that I decided to throw that thought awaychange my mind because a certain user would have never corrected my mental outpourings again.

hahaha.

I hope 'mental outpourings' transfer as well as I wantlated in the way that I intended into the English language.

I can understand it. I guess it would technically be 'My current train of thought'.