That question is impossible to answer. That depends really on date and time how popular a train is.

I would like to arrive in Munich on June 24th (Friday) so the train in Sweden would depart on June 23th (Thursday). 

I was hoping there’s maybe someone who travels in Sweden a lot and therefore could give helpful information.

It helps if you specify the exact trains you'd like to use, with departure times.

I understand:

-Highspeed train from Stockholm to Malmo at 11:21 on June 23rd

-Highspeed train from Stockholm to Malmo at 17:18 on June 23rd

Thank you :)

The 23rd of June is the day before Midsummer and it is one of the most hectic travel days of the year in Sweden. Just now there are seats available on all departures but I would recommend you to make you reservation rather soon.

Here you can make your reservation with SJ.

https://www.sj.se/en/home.html#/

Here you can make you reservation if you want to travel with Snälltåget who has night train to Hamburg/Berlin from Stockholm

https://www.snalltaget.se/en/berlin

If you need help how to get the reservation only with Interrail, please ask here.