Change filter's width

.hp-page__sidebar .site-sidebar{width:160px}

what is the css class to change the width of the filter form? I tried the css above but doesn’t work

If you mean listing filter form then please try this CSS snippet

.hp-form--listing-filter{
    width: 160px;
}

hi yevhen this solution works, but what is the css class for the listings beside filter form? I want to make it wider

If you mean sidebar then it has class hp-page__sidebar. But if you want to change its width then it is needed to change these CSS properties values flex-basis - CSS: Cascading Style Sheets | MDN and max-width - CSS: Cascading Style Sheets | MDN
It is possible to view which values of these properties it has now by using Developer Tools View and change CSS - Chrome Developers