My biggest mistake in language learning (1/2)

Some people believe that for a language learner the objective for speaking should be to be understood. They think that one should not dwell on one's accent if it is adequate to be comprehended. At the same time, there are plenty of individuals who advocate for studying phonetics at the beginner stages of language learning. I made a huge mistake by underestimating the latter idea...
A week ago, for the first time, I received constructive feedback on my speech based on almost 2 hours of pure convesation from a native speaker of English. He told me that although I was 100% understandable, and both my vocabulary and grammar knowledge was almost excellent, my accent was more obvious than I thought. Hence, I decided that this would be a perfect moment for me to delve into phonetics.
First of all, I understood the difference between pronunciation and accent. While pronunciation refers to the way of spelling the sounds, the word accent describes the general way of speaking, including rhythm, intonation, and the word stress. One can have a magnificent pronunciation yet distinctive accent. However, it does not work vice versa: one can not reconcile the outstanding accent and a deplorable spelling.
This drew me to the conclusion that it is vital to start working on one's pronunciation as early as possible.

Hello! I am aiming for a formal style of writing. Feel free to correct not only grammar mistakes, but also things that may sound unnatural. Thanks for your help!