Learn Italian: La vetrina del negozio è molto bella. - The shop's window is very beautiful.

Italian does not have an apostrophe-S structure for possession. Instead of saying "the shop's window," you always have to structure it as "the window of the shop." This is why the sentence connects the two nouns using del (of the).

Where exactly does the word del come from in this sentence?

del is a combined word made from the preposition di (of) and the definite article il (the). Because negozio is a masculine singular noun that uses the article il, they merge together into del.

Since vetrina and bella are feminine, why does the sentence use molto instead of molta?

In this sentence, molto means "very" and is acting as an adverb to describe how beautiful the window is. When molto is used as an adverb like this, it never changes its -o ending. It only changes its ending to match gender and number when it means "many" or "a lot of" and describes a noun, like in molte vetrine (many windows).

The word right before bella is negozio, which is masculine. Why is the adjective feminine?