Bonjour !
Verbs ending in -er belong to the first conjugation and form their present tense stem by losing the -er from the infinitive.
The present tense endings for -er verbs are: -e, -es, -e, -ons, -ez, -ent
1. Florence et Alima nagent. (nager)
2. Je joue au basket. (jouer)
3. Emile plonge dans la piscine. (plonger)
4. David et hugo jouent.(jouer)
5. Noémie nage.(nager)