Some of my friends connect -umi to nouns like in the examples below. In brackets are the meanings I caught through context.
varsoviumi (talk about Varsovio, look at pictures of the city and/or walk around in it)
telegramumi (chat or hang out using the messaging service Telegram)
matematikumi (do maths as a hobby, have fun with maths)
I want to know if this use of -um is grammatically correct, or considered playing with words / creative language?