Translation:I have never shaved, I am only ten years old.
''Nie'' always has to be behind verb. You can put ''się'' for example after verb and everything is fine ;)
This is incorrect punctuation, in English at least. There needs to be a coordinating conjunction or transitional expression between two independent clauses to use a comma. Alternativelty, the comma could be changed to a semicolon or the start of a new sentence. It should be changed to "...shaved, for I am..." or "...shaved; I am..." or "...shaved. I am..."
It is a completely fine sentence in everyday speech. We're not learning literature English or literature Polish.
What about I have never shaved myself...? I noticed that sometimes reflexive pronoun is necessary to translate zaimek zwrotny.
Only if it's correct in English, and as I was told, this would be really strange in this sentence.
Whereas in many languages words like "shave, wash, dress" are reflexive, this is not the case in English. Normally we simply "shave".
The only scenario where your suggestion would work is if someone has a servant to shave him, or goes to the barber every day, like in Western movies. But the rest of us just "shave".