The 3 lines at the bottom not working.

[TympanicFir8748]

Sometimes, I have seen people's 3 lines/recent apps button not working, this can be fixed by going to settings, then to the category "Apps" and then find One UI, force stop it and letting it start again. 

[Windroid]

Through the same route, go to the same app, storage, clear cache, and data and see if that helps

[lminvti · Accepted solution]

You can also turn swipe gestures.

[TympanicFir8748]

Use these comments to help too.

[Farai]

Lifesaver.... thank youu.

[JoseTheGreat]

This method works guaranteed.

(Sansung Galaxy A35 5G)

[ImInYourWalls]

What about for Samsung A14 galaxy???

[Gamaliel]

Thank you so much, it work for me! Yay!    I told my girlfriend I needed a new phone lol

[lminvti]

Not a problem at all, really glad it helped 😊

[BhuRan]

Thank you. It really worked