Sorry for being unclear. localhost:8080 is only the correct hostname and port if you defined this during the installation of RapidMiner in the step depicted below. Please try the healthcheck with the hostname and port you defined there.
In addition, on the screenshot you posted it states that the address "DESKTOP-Stefi/18.104.22.168:9990" is already in use which points to the direction that your RapidMiner Server is already running.
If this does not help at all perhaps you try to delete and reinstall RapidMiner Server?
From then on we could move on step by step to ensure everything is set up correctly.
most likely the cause for this issue is a lack of permissions. When i.e. no execute permission is given sudo returns a 'command not found' error. You may try to run
sudo chmod 755 rapidminer-server-installer
and execute the installation command again.
the reason for this issue is that RapidMiner Server tries to write row data with up to 20,000 bytes as a default. For some databases this limit may be slightly too high, especially when many columns with compact representation need to be written. In this case please modify default setting by addding com.rapidanalytics.db.max_rowlength parameter to your server configuration and reduce its value to i.e. 15K or 10K. Please do not use tiny values since for every row exceeding this limit an additional table is created, very small values therefor cause huge overhead during writing operations.
The section 'Modifying system settings' of our server administration guide shows how to apply parameters. It also holds a table describing advanced server parameters and their corresponding default values.
Yip, this is the best way. I did this a couple of times myself. Best is to make a fresh installation of RM Server at the same time although it is actually possible to change the configuration scripts of an existing installation as well (but is much more complex).
When reproducing your problem I managed to fix it by setting the permissions for this connection.
Would you please check if they are set on your machine?
Another question which might also be interesting here: How did you trigger this process?
From Studio by clicking on "Execute on Server" or from the Server Webinterface?
If you are running Windows and have it installed as a Windows Service, open up your Windows Task Manager, navigate to Services, and scroll down till you find the RapidMiner Server entry. Then right click and start. It can take a few minutes before you can access localhost:8080