Tempo Not Working

It is easiest if you upload the score so we can see what the problem is, but at a guess I suspect you may have changed the tempo in the Play Panel when what you really want to do is add tempo text.

You should add tempo text with the desired tempo and make sure the Play Panel tempo is set to 100%. The links I included above ahow you how.

Or perhaps by "it goes to 216 beats per minute without permission" you meant not right away but partly through the score. This could happen if you imported a MIDI file with lots of hidden tempo changes. To see these go to View --> Show Invisible, and then you can find and delete them as normal. (Right click on one and go to "Select > All similar elements to get them all in one go) .

Thanks for uploading the file. The problem arises because your tempo text uses a dotted crotchet instead of a normal (straight) crotchet which is not correct given your chosen tempo of 2/4 (and later 4/4).

You'll have to delete the tempo (and the one later in the score) and pick the correct (undotted) one from the Tempo Palette. You don't need to add it again after the 4/4, you only need it at the very beginning.

The reason for the 216 bpm is that your 2/4 time signature says "there are two beats in a bar and those beats are crotchets". When you use a dotted crotchet in the tempo you are NOT saying "144 beats per minute", you are saying "144 dotted crotchets per minute". A dotted crotchet lasts 1.5 times longer than a crotchet, hence the actual tempo is 144 x 1.5 = 216 bpm. You need to make sure that the note-duration you use in the tempo marking matches the beat value set in the time signature.

Pizz. (pizzicato) playback is explained in the Handbook, but I see you've already had a go at doing it. The problem is that you haven't applied it to the right voices. If you're not sure about voices then have a look in the handbook.

You currently have only applied the pizzicato effect to voices 2 and 4.

You need to right-click on Pizz., open Stave Text Properties, and apply the effect to all four voices:

Also, the 2/4 bar at the very beginning isn't strictly necessary. If you want you could do it like this:

Notice that the first bar only has two beats (i.e. two crotchets) while the rest have four. This is called a "pickup measure" (or anacrusis). The Handbook tells you how to do this here:
https://musescore.org/en/handbook/measure-operations-0#properties