All versions of Forge just crash.

[Oletrix]

Hi. Don't know really were to begin so I'm just going to spew out data.

I'm trying to get forge running on Ubuntu 18.04.2 LTS. 
I'm new to Linux and could put a Windows 10 SSD into my system but I'm very determined.

I'v bought the game couple days ago, wanting to play some modded v. of MC
Started reading, installing forge, changing the java version.
And it worked, once, not detecting the Craft of Titans mod.

But it didn't run aver again even on a clean installation of MC.

And I've tried a couple of forge versions: 1.14.. 1.12.. 1.7.. 
I'm pretty sure that just installing a different v. on top of the previous one didn't work as they did not even showed up in the launcher.
Deleting the .minecraft folder isn't probably the right way to uninstall.
I've spent to many hours already trying to find some info on the internet, but all the post ar from 5 or more years ago on older versions or about windows forge.

Any way, here are some screenshots:

And hopefully some logs:
<script src="https://gist.github.com/Oletrix/12d0c1144649506266c6f13170944e25.js"></script>

Thank you in advance to anyone that has the patience to help me out.

[Oletrix]

  On 7/20/2019 at 8:19 PM, diesieben07 said:

Use Java 8.

Expand  

$ java -version
openjdk version "1.8.0_212"
OpenJDK Runtime Environment (build 1.8.0_212-8u212-b03-0ubuntu1.18.04.1-b03)
OpenJDK 64-Bit Server VM (build 25.212-b03, mixed mode)
 

still not working. what am I missing?

<script src="https://gist.github.com/Oletrix/014330d4594b14370adc1be9b05458b5.js">log</script>

Edited July 20, 2019 by Oletrix

[Oletrix]

  On 7/20/2019 at 9:13 PM, diesieben07 said:

The log you posted shows you using Java 9 or newer.

Expand  

sudo update-alternatives --config java
[sudo] password for majonez: 
There are 3 choices for the alternative java (providing /usr/bin/java).

  Selection    Path                                            Priority   Status
------------------------------------------------------------
  0            /usr/lib/jvm/java-11-openjdk-amd64/bin/java      1111      auto mode
  1            /usr/lib/jvm/java-11-openjdk-amd64/bin/java      1111      manual mode
  2            /usr/lib/jvm/java-12-oracle/bin/java             1091      manual mode
* 3            /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java   1081      manual mode

Press <enter> to keep the current choice[*], or type selection number:
 

Any good guides on how to get the proper java installed and running?