Learn Dutch: Ik lever hetzelfde product, mits u met de prijs instemt. - I deliver the same product, provided that you agree to the price.

mits (provided that) is a subordinating conjunction. This means it introduces a subordinate clause and pushes the conjugated verb (instemt) to the very end of the sentence.

I know stemmen means "to vote". How does it mean "agree" here?

The verb here is actually the separable verb instemmen, which means "to agree". It is usually paired with the preposition met (with/to), which is why the sentence says met de prijs instemt.

Why is instemt written as one solid word here? Aren't separable verbs usually split?

Separable verbs split in a standard main clause (like ik stem in). However, because mits forces the verb to the end of the subordinate clause, the separable prefix (in) and the verb (stemt) are joined back together into a single word.

Why do we use hetzelfde instead of dezelfde for "the same"?

The Dutch word for product is a het-word (het product). You must use hetzelfde for singular het-words, while dezelfde is used for de-words and all plural nouns.