Stop automatic start in W10 cannot be set

I would like to be able to start up my computer WITHOUT avg automatic starting. When I want to arrange that in W10, Apps, Start-up, I cannot (= canNOT) put the slider in W10 to OFF, next to the avg-launcher.
How to be able to start up W10 WITHOUT avg automatic starting?

Greetings,

Have you tried to disable the startup item from Task Manager?
Using the startup tab of Task Manager, you can easily prevent an application from starting with your Operating System. It is very easy - just right click the desired application and pick "Disable" from the context menu.
Thank you.

Greetings,

We apologize for the inconvenience.
AVG AntiTrack and AVG Secure Browser starts automatically at startup.
May I know which AVG product is automatically start?
Thank you.

Greetings,

We apologize for the inconvenience.
AVG AntiTrack and AVG Secure Browser starts automatically at startup.
May I know which AVG product is automatically start?
Thank you.

Upon checking the provided url in our end, it works fine, JJ.
You can try accessing this site in a different browser.
However, here are the steps to disable the AVG protection temporarily :
Right click on AVG icon in system tray (near date & time, at bottom right corner) - click on toggle bar beside protection to disable it. 
Alternately, you can manually disable all AVG components through Computer, Web & Email, Hacker attacks, Privacy, Payments tiles that are available in AVG program.

Thank you Dinesh.
And yes I am fully aware of the possible vulnerabilities when I put AVG in 'not automatically start-up mode'.
The article you refer me to cannot be opened because it is on the support center of AVG-company and that is being revised. So I get a web screen saying "We'll be right back". The AVG Support Department is presumably busy with an overhaul of the support-website.
Ar there any other links to be used?

Thank you for clarifying, JJ.
It isn't recommended to disable AVG at startup. Reason being, there are possibilities for your system to be prone to attacks at startup. 
However, you can try to disable AVG protection temporarily by following the steps in this article, to check if it allows you to install the other program.

Good evening,

I am using AVG Internet Security, software version 21.3.3174.
Suitable for 10 PC's.

In W10, Start up Apps I see:
AVG AvLaunchcomponent. This app stays at On, even when I click it to get it to Off.

I do hope you can help me with this. :-))
Because I want to have the choice myself about how to operate my PC's.
(Also because I need to install another program that needs to make a connection to their company website to do a first activating registration.)
Thanks in advance for your help,
Sincerely…