Do I need a drop down list?

If they are in the forum, then they should post in that forum automatically. Where are users posting? Are you using a shortcode?

A link to a live example would be useful.

https://byggdoktor.com/extranet/diskutera-och-tipsa/
Password is BD2017. At the bottom you will find the drop down list.

I use shortcodes.

ok, so what shortcodes are on that page please

[bbp-topic-index]

[bbp-topic-form]

[wpdm_package id=’1494′]

so change

[bbp-topic-form]

to

[bbp-topic-form forum_id=$forum_id]

where $forum_id is the ID number of the forum, you can find this in dashboard>forums>all forums

eg

[bbp-topic-form forum_id=2927]

Then the ability to create a new topic disappeared from the bottom.
There was a button on the top created in bb press style pack. For some reason it disappeared.
So there is no opition at the moment to create a new topic.

so what do you have now as shortcodes in that page?

Now it looks like this.

[bbp-topic-index]

[bbp-topic-form forum_id=$forum_id]

[wpdm_package id=’1494′]

ok, you have to replace the ‘$forum_id’ with the actual forum ID as stated above

Aha. Success!
Thank you very much.