mitmachen
to join in
To take part in a shared activity, game, or campaign; to participate.
Wenn wir aufräumen, müssen alle mitmachen.
When we tidy up, everyone has to join in.

to join in / put up with
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to join in
To take part in a shared activity, game, or campaign; to participate.
Wenn wir aufräumen, müssen alle mitmachen.
When we tidy up, everyone has to join in.

'Mitmachen' (to join in / to put up with) is a separable verb. The prefix 'mit-' goes at the end in a main clause, while in a subordinate clause it remains attached to the verb. In the infinitive, 'zu' goes between 'mit' and 'machen'.
Bei diesem Projekt mache ich gerne mit.
I'm happy to join in with this project.
The verb is made up of the prefix 'mit-' and the verb 'machen' (to make/do). The prefix 'mit-' means 'together with others', which logically explains the basic meaning 'to participate'.
Alle Kinder im Park machen beim Fangen-Spielen mit.
All the children in the park join in the game of tag.
If you want to say which activity you are taking part in, you use the preposition 'bei' followed by the dative.
Willst du bei unserem Spiel mitmachen?
Do you want to join in our game?
The colloquial meaning 'etwas ertragen' (to endure something) always refers to something negative and needs an accusative object. The main meaning 'teilnehmen' (to participate) refers to an activity and can also stand without an object.
Diesen ganzen Stress mache ich nicht länger mit!
I'm not putting up with all this stress any longer!
to experience
'erleben' and 'mitmachen' can both mean that you are present for something. However, 'mitmachen' is used especially when you actively take part in a shared activity, for example a game, course, or project. 'erleben' is broader and emphasizes the personal experience, even if you are not actively doing anything. So you can experience a thunderstorm, but you cannot really 'mitmachen' a thunderstorm. Learners confuse the words when they only think of 'being there'. As a guide: 'mitmachen' fits active participation, while 'erleben' fits an experience.

Mein Kollege macht heute beim Erste-Hilfe-Kurs mit.
My colleague is joining in the first-aid course today.
Auf der Klassenfahrt haben die Schüler einen starken Sturm erlebt.
On the class trip, the students experienced a strong storm.