I was having some trouble with when to use different forms of verbs, but then I found a pattern.
The -en ending (horen, koken): I think it is used for plural you or they, like "They are cooking" or "You are hearing."
The -t ending (hoort, kookt): I think it is used for singular you or they, or we, like "You cook" or "We hear."
The "natural" ending (hoor, kook): I think it is used for I, like "I cook" or "I hear."
I hope this is helpful if you're struggling with that too!
Very close! Here is a quick chart of the verb conjugations for cook:
I cook: Ik kook
You/he/she/it cooks: Je/hij/ze/het kookt
You(plural)/they/we cook: Jullie/ze/we koken
For a full chart and more explanation check out these Tips and Notes: https://www.duolingo.com/skill/dn/Basics-1/tips-and-notes