You may have to pay a fine when you leave, and it will become much harder to get any future visa.
What happens to your sponsor depends on how he sponsored you. In Germany there is something called a Verpflichtungserklärung which is a promise by the sponsor to reimburse the German state for all costs of your overstay and removal. If he signed that, they'll demand that cost. If he hat to put down a deposit, the cost is not limited to the deposit.
If you qualified for a visa without a Verpflichtungserklärung this does not apply.