your sentence structure is needing some punctuation, it's tough to sift through your post.

That aside,

look up frequency charts and the differences of subtractive and additive eq. Look up signal chains, and the importance of effects in the chain.

Understand how you can better utilize stereo effects, understand how you can best utilize dynamic effects/tools, understand how you can best utilize frequency control (this is what you seek from your post), understand how to best utilize instrument position and stereo width (mono/stereo, panning)



You need the mindset of "how can i best fit this instrument, with this frequency range, into my song?"

The key will also effect how your eq responds.

I also know that this chart is for acoustic instruments, but the range in which frequency and vibrations go, the timbre is the only thing that's different when it comes to synths/natural instruments. You can have a synth and an oboe occupy the same range. Reason being, some instruments work better in certain keys than others and are forced into spotlight at times.

There's probably nothing new to what you've been told, but the research you should seek and the questions you should ask need to be more pointed with understanding of yourself and your skill.

I'll always suggest this, find some one irl to help you. The forums can only do so much.
lastly, do your own research.

Combine all this information i've given you, and you should, hopefully, be ready to rock and roll and eventually learn for yourself and seek answers to the problems.