Keeping up with C++ using common practice problems and core C++ concepts. I found The Cherno Project to be absolutely invaluable to get back to the rhythm of my C++ days from yesteryear.
A general recap of core Python 3 Concepts from basics to advanced with focus towards PEP8. I really find sentdex's guides and tutorials very helpful in going from basic to advanced level. This should be a must subscribe for every python developer imho as should the PEP8's words of wisdom.
I intend to keep this a work-in-progress for all my language specific coding practice sessions. Please note, this may not be the best or the most exhaustive learning resource for these languages. Instead, everything here is tuned to my general comfort level and experience with each language.