Not a productive day.  or "An Unproductive Day"

I can't exactly explain why, but these two sentences sound better:

Today has been a lazy day. I haven't done anything useful.

Today was a lazy day. I didn't do anything useful.

I slept in and didn't get got up at until about 11, and then ate eat a bit. I weighted weighed myself and realised I hadn't gained anything (trying to put on some weight). Then I spent some time watching my favourite youtube channels, I had to catch up with it. or "Then I spent some time catching up with my favourite youtube channels." By the way, Fun for Louis is awesome! Then Me and my girlfriend then (there is nothing wrong with the sentence you wrote. I just changed the word order so that you didn't start two sentences with the word "Then". It's just a stylistic choice) decided to watch Murder on the Orient Express which is now showing at the cinema on the screens. I know, it's almost finished screening now, but still. So we started preparing, I bought tickets for(?) 19:05 session at Altufevskiy mall.

We got out of the flat and headed for a pet shop. After we were done there we needed some groceries. Later When we finally arrived at the cinema, I had got a double whopper with cheese. I can't resist burgers =) After that we played a couple rounds of an air-hockey. I was a mess! Finally the movie began!

I liked it. I mean it wasn't brilliant but I had been (?) preparing for the worst. I'm giving it 7/10. By the way, I didn't guess who the murderer was (?) both these sentences are fine

Basically it that was the my day. I hope you will correct my mistakes and maybe help to diversify my speech. Thanks!