tToday, I have practiced my knowledge about the tenses in particular the future tenses.

Can also say: "Today I put my knowledge of future tenses into practice."

To get used to them, I would like to write down some examples which I came up with.

I would be delighted if somebody could give me a hand and correct these.

Can also say: "somebody could lend me a hand"

I hope I won't do thatmake many mistakes with these sentences.

When I look outside I can't help myself but think that it's going to rain.

Normally I 'm not that hungry in the afternoon, but today I have a dark mood.

Would replace with "dark mood" with something else, since it is not clear what you mean. For example, "today I feel sad/disappointed/tired/lethargic/etc." or "today I am feeling down."

I know that not all of my sentences are using a futureuse the future tense, but this will change with my next one.

A friend of mine is visiting me in half an hour.

Can also be: A friend of mine is visiting (me) in half an hour.

But sometimes I play like a genius, so my friend often thinks I am going to be one.

Grammar regarding future tenses

You would simply write: The future tense.
or more complicated.
The grammatical structures of the future tense.

today I have practiced my knowledge about therevised the grammatical tenses, in particular, the future tenses.

'practiced my knowledge about' doesn't make sense but it would just be the word 'revised' if it did :)

To get used to them I would like to write down some examples whichthat I came up with.

'that I came up with earlier.'
'Here's one I made earlier' is a popular phrase in English, it goes back to TV shows about crafts, instead of filming someone painting a box for example they would just say 'Here is one i made earlier' and bring out a box that had been painted already.

I would be delighted if somebody could give me a hand and correct these.

give me a hand/help me out
both work.

My train leaves at 7:15 pm.

More formal = my train is scheduled to depart at 7:15pm

But I am meeting my friends before at the train station.

avoid starting a sentence with 'But', the same goes for starting a sentence with 'And'. It would be best to write: My train leaves at 7:15pm, but/and I will be meeting my friends before that at the train station.

But also implies that the train leaving at that time is a problem because you will be with your friends instead.

I hope I wdon't do thatmake too many mistakes within these sentences.

'I hope i don't mess up these sentences.' = Colloquial.
'Hopefully these sentences are grammatically correct.' = Neutral.

When I look outside, I can't help myself but think that it's going to rain.

Just at this moment, I decided I will have to go to the fridge and get some tasty food.

you would write 'will have to' if you have already mentioned being hungry.

Normally I m not that hungry in the afternoon but today I have a dark'm in a bad mood.

But today I'm in a weird mood.
But today I'm in a dark place. (mainly used for depression)
But today I'm starving for some reason. (potentially offensive to people who are actually starving but people say it anyway)

I'm looking forward to reading my new book which I got yesterday.

I know that not all of my sentences are using a future but this will change withwritten in the future tense but my next one will be.

(How do I say in English that not all my sentences are "acting" in the future. I can't remember a fitting word. )

not sure what you mean by 'acting'.. all of my sentences are hypothetical?

A friend of mine is visiting me in half an hour.

'in about half an hour' sounds more casual but your's works too!

I hope he will also brings his chessboard.

I don't think that I will ever become a famous chess player.

technically correct, ever makes it sound better!
or 'I doubt I'll ever be a famous chess player'
'I doubt I'll ever become a Grandmaster'

B, but sometimes I play like a genius so my friend often thinks I am going to become one.

haha. Same goes again for starting the sentence with 'But'.

I don't think that I will ever become a Grandmaster, but sometimes I play like a genius so my friend often thinks that I am one.

Thank you for correcting :))

no problem :)
Thanks for the corrections.
Thank you for correcting my work.