Hi
I don't know about certifications, but of course there are many sources out there, given the cryptocurrencies deal with many many fundamental topics worth their own course (computer science, cryptography, games theory, economy just to mention the major ones). Laying on those, any cryptocurrency has its peculiarities, and this again open a big landscape. So I guess first you should understand what you want to improve (I suppose you already have a basic knowledge of the tech).
That said, my opinionated hint is Foundations of Blockchains by Tim Roughgarden:
https://www.youtube.com/playlist?list=PLEGCF-WLh2RLOHv_xUGLqRts_9JxrckiAno certification, and not all the lectures have been released yet (my educated guess is half of total have been; it's partially funded by IBM grants so I have no worries about its completion) but it's a very high bar course (university level) and free of charge. It deals with computer science side of blockchains, the only resource I have found going very deep on state machine replication flavours, BFT, longest consensus, PoW e PoS anti-sybil leader election strategies, and more. All of that with agnostic style. It's a long term effort, and you won't master a specific cryptocurrency after it, but you'll have powerful knowledge tools to analyze the many promises of this field, and why not, to choose which technology to devote to.
my2c
Hello everyone, I plan on improving my CV by adding some cryptocurrency courses . Since one can gain a certificate online, I want to use my free time to study a course; [...]