>>Thank you very much for all the links and advice!<<

I am happy I could help.

>>Your post "Twitter Exodus" has been a godsend these days and I will definitely read it again today when I write my first post.<<

Yay! I wish you luck with the first post.

>> I found the landing page for "Love Is For Children" right away and I bookmarked it on my browser, same as "A Brief Guide to The Avengers". Maybe I should use memories for this? <<

Some people like bookmarks. I use Memories for things I want to be able to find again. Most of that's in my How To section.

>> I read your new poem and I really liked it! I love how you portray JARVIS (and Bruce & Hulk).<<

Thank you. I think they need more love and care than they usually get.

>> I used your december followfriday posts to find some active communities to subscribe to, <<

I'm glad you found some that appeal to you.

>> and I bookmarked a lot of writing ones that I will subscribe to/join when I feel sure enough in my writing skills (English is my second language) to post some of my stories.<<

If you hadn't told me, I probably wouldn't have noticed that English is your second language.

Beyond that, though, the way to get better at writing is to write things. Start small if you like -- there are lots of drabble communities, and allbingo can be played with any size of card or fill. About half my fills this month for Public Domain Day Bingo are haiku. All of them are short because my Poetry Fishbowl theme on Tuesday was "short forms."