Hi,
In a nutshell yes I have been able to raise my GFR, I managed GFR48 to GFR63. I started 13 years ago with Zero kidney function after AKD, my kidneys stopped working for 18 hours before it was noticed. It took strict management of diet and life style, so strict it became rediculously difficult having to watch everything I consumed, micro managing everything. I have since relented to a more suitable diet and watched my GFR slide. Doing it my way I'm able to keep my GFR relatively stable now with a small decline over the last 13 years. Kidneys decline with age anyway. I'm sitting on GFR 38 at present and expect my kidneys will last the distance at my current state. As the ravages of time are getting me I have relented and allowed my Dr's to mitigate my kidney health, a little. I won't do anything that can impinge on my kidneys, but dealing with other significant health issues I have to be mindful of their needs as well. It's all about personal managment. I always have blood drawn at the same time of day after doing the same things each time to give a consistant result. I did everything I shouldn't once to see what would happen. An urgent call from my Dr resulted from my rapid GFR decline, I couldn't tell her what I did but it got the response I wanted. Now I'm watched like a hawk and getting more attention than previously. Kind of nice to have her focus now.
There are many things that contribute to kidney function or not, without knowing the circumstances there is not much that can be said, but yes you can raise your kidney function.
Cheers