I am tired of Romance languages, and I am just learning a language to have fun and just to speak 2 languages or more. Will Eastern European languages be easy to learn?

Examples:

Polish
Slovak
Slovene
Czech
Hungarian
Russian
Serbian
etc...

I really love to learn foreign languages , therefore, made lots of efforts on those for years.
I can speak Chinese,Portuguese,Japanese at present.
Furthermore,I really want to put my mind to learn eastern european languages ,like Polish,Czech,Bulgarian,and etc.
Is it worthwhile to spend time learning one of those languagues?
What would I benefit from such a learning process?