Learn Italian: Per quanto tu lo riavvii, c'è ancora il virus. - No matter how much you restart it, the virus is still there.

Here, per quanto acts as a concessive conjunction meaning "no matter how much" or "however much". It introduces a condition that you would expect to change the outcome, but doesn't. Conjunctions that express this kind of concession (like benché or sebbene) generally require the following verb to be in the subjunctive mood—in this case, the present subjunctive riavvii.

Why does the verb riavvii end with a double 'i'?

The infinitive is riavviare (to restart). If you remove the -are ending, the stem of the verb is riavvi-. Since the regular present subjunctive ending for the tu form is -i, you add that directly to the stem, resulting in the double vowel riavvii.

Italian often drops subject pronouns like tu. Why is it explicitly included here?

In the present subjunctive, the conjugated verb forms for io, tu, and lui/lei are usually identical (all three are riavvii for this verb). Using the pronoun tu is a common and necessary way to remove ambiguity so the listener knows exactly who is doing the restarting.

Could the pronoun lo be attached to the end of the verb instead?