Learn Croatian: Poštujem tvoje stajalište, ali se ne slažem. - I respect your standpoint, but I don't agree.

It comes from the verb stajati (to stand) combined with the suffix -lište, which usually denotes a physical place like parkiralište (parking lot). In this sentence, it is used metaphorically to mean a standing place, or a point of view.

What happens if I drop the word se and just say ne slažem?

It completely changes the meaning. The verb slagati without se means either to stack things or to tell a lie. To mean to agree or to get along, it must be used as the reflexive verb slagati se.

Why is the reflexive pronoun se placed before ne slažem rather than after it?

In negative reflexive verbs, the short word se very commonly slips right before the negation ne. You can also say ali ne slažem se, which is grammatically correct, but placing se before the negative particle flows very naturally in everyday speech.

Why is the verb poštovati conjugated as poštujem instead of poštovam?

Verbs ending in -ovati follow a specific pattern where they drop that suffix and add -ujem for the first-person singular present tense. You likely already know this from verbs like kupovati (to buy), which becomes kupujem, but it is an easy pattern to slip up on when speaking quickly.