Slow (but working) wifi connection with Ubuntu 18.04 Dell Vostro 5490

[efh89]

Hi everbody
I noted that my (still working) WiFi connection started being rather slow recently.
I attached the wireless info file generated by the e wireless info script.
I am using Ubuntu 18.04.4 on a Dell Vostro Computer 5490.
I hope I gave you all the information you need to give me some hint to fix this issue.
Thank you

PS
When I installed Ubuntu (6 months ago) I had serious problems in making the WiFi working.
After several attempts it worked with some trick found on internet, that unfortunately I do not remember...

[chili555]

Please run:

sudo apt purge backport-iwlwifi-dkms

Reboot and let us hear the result.

[efh89]

I used the command suggested by chili555 and I noted a significant improvement in the wifi speed.
I will test the network for few days to check that everything is fine and put solved in the post title.
Thank you so much