both

https://wpforo.com/wp-content/uploads/2018/12/Website-Style-Customization.png

Click on that, find the Additional CSS menu, open and and put this CSS code:

.wpforo-widget-content p.posttext{display:none;}
.wpforo-widget-content p.posttitle{font-size:12px; margin-bottom:3px;}
.wpforo-widget-content .postuser{font-size:12px; }
.wpforo-widget-content li{border-bottom:1px dashed #999999; margin-bottom: 7px}

https://wpforo.com/wp-content/uploads/2018/12/Add-Custom-CSS.png

Don't forget, save it using the top blue button, then delete all caches and press Ctrl+F5 before checking.

in the custom css code in styles didnt work

I don't recall there being filters for the sidebar widgets. You could try hiding the reply text with CSS.

#wpf-widget-recent-replies .wpforo-list-item-right p.posttext {
visibility: hidden;}

And i will explain you why,

if there you wait for a resonance from someone , yes or no, for example,

you will read it on the widget and you will no click it, so ,

if you ckick it maybe you reply too.

This means less pageviews and less time on site, so less ranking.

I think this is what you are looking for?

Set Extended Layout - Recent posts to "Expanded"

Set Extended Layout - Number of Recent posts to "1"

Set Recent Posts Display Type to "Topics"

Recent posts will look like this: https://prnt.sc/ltx9mz

Forum view will look like this: https://prnt.sc/ltxap2

I want the part of the post with the white letters that is visible ,

under the topic title not to be visible.

Please leave your forum URL, and also please try to explain using another screenshot what exactly you need to change. 

No matters what settings i set is not working.