The rule for the Simple Present is quite simple.

The verb stays the same with every person except at the rd person singular


At the third person singular, the verb can be written in 3 different ways

With most verbs, the verb only takes an at the end

When the verb ends with "Y" preceded by a consonant, you replace the "Y" for

When the verb ends with s, sh, ch, x, z and o, you put

There are only two exceptions: "be" and "have"

Be becomes , ,

and have becomes