"Nem kiabálok."

Translation: I am not shouting.

[KbearrK]

Yell and shout should both be acceptable.

[Tamara207217]

report if it's not

[Maa249530]

NEM KIABÁLOK

[LanguageSurfer96]

ÉN SEM!!!

[Emile-_-]

Is "kiabálni" here composed of "ki+abálni" or is it a verb without particle?

[MrtonPolgr]

The latter. There is a rare and probably unrelated abálni verb, though.

[PeterHoope1]

Yell and shout mean the same thing

[Nab918927]

So with multiple vowels in a word which one is used to determine the suffix of the verb?

[MrtonPolgr]

Typically the last one. With i, it's common that preceding back vowels override it, with é, it's like both can be accepted depending on the speaker.