I swear by coaches/instructors in other areas of my life, but haven’t had much luck with language teachers. I’ve had private teachers with middling success (great at correction, bad at longer term planning), and found I had more improvement by self-studying.
In the interim year since, I've continued the 1:1 lessons and obviously improved a lot naturally as well. I've had multiple people ask me if I was half-Japanese (I'm not) and other people tell me "it would be rude to say you're good at Japanese; it's more apt to say you can just speak it normally." Other people don't mention it at all and just treat me as they would any other Japanese person. (Which sometimes backfires because they use high diction or very arcane expressions and idioms.)
For me, the key was finding a 1:1 teacher that I could meet 2-3 times a week (we met remotely over Skype), and I mixed basic conversational practice in along with targeted grammar study. iTalki is where I first started down this path of 1:1 tutoring, (where I found my first few teachers), and it's worked out great for me.
I can recommend Yuri T on iTalki.