I don't think you need to learn them all at once, you could start learning a basic command and how coordinates works (if you don't know yet), the /tp and /setblock commands sounds like a good start, don't be afraid to experiment what thing does what, go wild!

From there you can start learning more advanced commands but only the ones you need. Want to make every zombie on the map fly like a balloon? learn the /effect command and target selectors. Need something to happen when a block is placed somewhere? learn the /execute command.

There are tutorials which teach specific commands and the minecraft wiki also helps a lot.

Also: chain command blocks are very useful ;)

i would suggest this tutorial, by bertiecrafter

This isn't my video, but what really helped me learn command blocks was a series by SLICEDLIME. it's on YouTube, and goes over the important commands (clone, execute, fill, etc...) you should check it out!