Mones plans pour le week-end

The word usually is pluralized when you plan several activities

Le vVendredi dernier, j’ai fini mes examens pour devenir avocat.,

le vendredi = on FridayS (indicating something regular)
vendredi dernier = last Friday
Unless you really want some stylistic effect, it would be much better to include the "donc" clause with the main one in a single sentence

Ddonc, ce week-end, je me détends.

Hier, je'ai jouaisé aux jeux- vidéos et ; aujourd’hui je v'irais à la gymnase et je ferai le[salle de sport ?] et au sauna -: c’est parfait pour se détendre et de-éstresser.

Main action of the narrative = passé composé => j'ai joué

; to avoid repeating "et" too much

"vidéo" behaves like an invariable adjective in "jeux vidéo"

If you mean going to the gym to work out, then it would be "la salle de sport". "Un gymnase" is a much bigger place with sophisticated equipment for athletes and gymnasts, like pommel horses, usually a track outside etc

I've never ever heard "faire du sauna"; people say "aller au sauna"

Hyphens are almost never used to indicate complements or examples in French. Depending on the context, commas, parentheses or (semi)colons are used instead

The dé- prefix in relatively new constructs is a exception, the <e> has an accent even in front of combinations such as <st>