“level of the oceans” or “ocean levels”. The oceans are connected so they have the same level subject only to tidal variations. However, since the level changes over time it makes sense to say “ocean levels”.

1 and 3 are natural. For 2, more standard is ‘relate to’, not ‘relate with’. ‘Relate with’ exists but is rarer and traditionally has a different meaning (interact). E.g. ‘I relate well with my in-laws. ‘ (I get along with them. I can communicate easily with them.) Perhaps your use of ‘relate with’ is growing and has achieved regional acceptance in some parts of the English-speaking world but it definitely sounds unnatural to me.

Looks good, Javier!

Yes they are readily understandable. There are many ways to write each sentence and each and every English speaker or writer will have their own preference. For sentence 2 "RELATED TO TECHNOLOGY" is the natural way.