I do not have ano intention tof completely eraseing my accent; instead, I just wish to pronounce all words in the right way, using intonation and stress correctly.

"I have no intention of [doing xyz]" is a very common expression.

Actually, I believe that B2 level proficiency is the best starting point for determined accent learninglearning to improve one's accent.

"determined accent learning" kind of sounds like you are determinedly learning to have more of an accent. "learning to improve one's accent" makes the intended meaning clear.

When one's level is lowerAt a lower level, it would be quite overwhelming to combine studying pronunciation with learning basic vocabulary and grammar.

Not incorrect, but this is more natural.

Hence, I do not regret about not delving into this topic earlier.

"Regret" is a transitive verb, so no need for "about." You could optionally also say "Hence why" without the comma.

However, now, I am exceedingly motivated to do it; I aim for at least an hour of daily practice.

No need for the double comma - you could also say "I am now..."

Today I spent a several hours practicing the ''th'' sound, and I can already feel the progress.

"Several" is never preceded with an article.

I am sure, of course, that there might beis/are a plethora of other confusing sounds.

There's a contradiction between "I am sure" and "there might be"—are you sure or not? Whether to use is/are in this case is a bit tricky. "is" is technically correct, referring to the singular "plethora", but you'd likely hear a native speaker say "are", referring to the plural "sounds."

Additionally, I want to obtain more knowledge about different mimicking techniques, —for instance, shadowing.

You can use the em dash like I did, or a colon.

I am cognizant, nNevertheless, that for now I mainly need to focus on learning IPA sounds.

"Cognizant" is a word people mainly use when they need to "watch out" for something. e.g. "I am cognizant of the risks, but I will do it anyway."

It could open me a lot of doors for me, and make my learning way much easier.

You can use "way" (casual) or "much" (neutral), but not both.

I dot is not have anmy intention to completely erase my accent;: instead, I just wish to pronounce all words in the right way, using intonation and stress correctly.

My objective is to make my accent unobtrusive, master: improving my pronunciation to thea level where native speakers know that I am a foreigner, but are not quite sure where I am from.

When one's level is lower, it would be quite overwhelming to combine studying pronunciation with learning basic vocabulary and grammar.

Aand vice versa,; when one has C1 level proficiency, the entrenched speaking habits would demand much more time and effort to be changed.

This may not have been the division of sentences you were after. If so I apologise.

Hence, I do not regret about not delving into this topic earlier.

However, now, I am exceedingly motivated to do it; I aim for at least an hour of daily practice daily.

I am cognizant, nevertheless, that for now I mainly need to focus on learning the IPA sounds.

It could open me a lot of doors,be a big help and make my learning way much easier.

I don't think 'could open a lot of doors' works here is more that it provides you with more opportunities in future and does not seem to fit what you are saying.

I do not have an intention to completely erase my accent; instead, I just wish to pronounce all words in the right way, using intonation and stress correctly.

Today I spent a several hours practicing the ''th'' sound, and I can already feel the progress.

I am cognizant, nevertheless, that for now, I mainly need to focus on learning IPA sounds.

It could open me a lot of doors for me, and make my learning way much easier.