Try Swiping your hand across the screen from left to right.

 

there isn't a timer setting. a short click is home, a long/longer press is Assistant. If you simply click it and it STILL brings up Assistant, then either there's a software glitch, or your home button is sticking.

 

You could take screenshots using the assistant also.

 

Sounds to me like the button is faulty- whether damaged (like liquid interfering with the function) or it's malfunctioning. Best to get it inspected/repaired.

 

Just go into Settings then Apps and in the upper right corner vertical 3 dots. Click and restore app Settings on your device. When done, restart your device and make the necessary changes to particular apps if necessary.

 

I've given you the appropriate information to address the issue. If you have eliminated software as being the problem, then the hardware is the only remaining possibility. Either get the phone repaired, or replace it via warranty/insurance- whichever is applicable to the issue.

 

Press home once = last 'home' screen you were on; press home again to go to the "home" home screen. You can also disable Google Assistant, if that's what you really want to do.