Yeah, this is a pretty good resource. That aside, I guess you need some awareness of what relative clauses in Japanese look like. That is, you need to know that if you find a verb or adjective in the end-of-sentence plain form in the middle of a sentence, then you need to realise that it’s a relative clause. Complex Japanese sentences are like onions: there are little core components (relative clauses) that you’ll find near nouns, and they expand outwards from there. They grow larger towards the right, typically, with every smaller relative clause modifying the next noun on the right. For example, here’s a sentence from The Rising of the Shield Hero, Volume 18:
出された飯をもりもりと食べる食欲魔人を見習って欲しいもんだ。
Here’s how I broke it down:
That’s essentially what you have to learn to do. It takes time and practice, but I figured providing an example might help you get an idea. Aim to see sentences as a series of blocks by the time you’re finished parsing them in order to get a feel for their overall structure. Over time, you’ll get better at it.