In my last blood test, I have high levels of B12 (950mg). What this mean?

There is no. Consequence of an elevated B12 level. It is a water soluble vitamin.
Nothing. This is a bit above the reference range but these ranges are actually set up so that several percent of folks fall outside. This used to be considered helpful in the diagnosis of proliferative diseases of marrow but in this era of genetic studies it's of historic interest. If you are otherwise healthy, i would not give it another thought.
Diet high in B12. I am not aware of any disease process that results in high levels of b12. Most light there is an abundance of B12 in your diet or dietary supplement.