Brief Answer:
Search the cause

Detailed Answer:
I read your question carefully and I understand your concern.

The first step in treating a neuropathy is searching for the cause. If there is a correctable cause then addressing it may solve or at least improve the issue. Neuropathy can have many causes, diabetes is one of them but there may be others. It may be due to nutritional deficiencies, electrolyte abnormalities, thyroid or other hormonal dysfunctions, rheumatological conditions, nerve compression, liver and kidney conditions etc.

So if no tests have already been done some blood tests for the above mentioned issues as well a test called nerve conduction studies should be done.

If such tests have been conducted and the cause couldn't be identified (can happen in 25% of cases) then it is a question of addressing the symptoms, trying to alleviate them. Of course it would be useful if you could say something about your symptoms, I suppose it must be in the form of abnormal sensations, but there may be other manifestations.
The most common medication to address such symptoms would be anticonvulsants used for neuropathic pain such as gabapentin or duloxetine.

As for Nervestra which you inquire about it is a compbination of vitamins and other supplements found also in everyday food. So it shouldn't perform any miracles unless there is a nutritional deficiency at the root of the neuropathy. There are no scientific studies to prove its efficacy. It is safe though, so there is no harm in giving it a try.

I remain at your disposal for other questions.

---