Hi @vini13
Try using the tablet's WiFi as close as possible to the network router in your premises i.e. <10cm and check if it works OK and that it maintains a stable connection.
If it works OK it may be a loose [https://rounded.com/samsung-galaxy-tab-a-8.0-2019-sm-t290-sm-t295-holder-wifi-antenna-gh81-17262a.html?sl=en|WiFi antenna] connection that is the problem, (supplier example only to show what the antenna looks like)
Here's a teardown [https://www.youtube.com/watch?v=erCsSXLOnAI|video] for the tablet that may help.
The antenna can be seen being removed from the tablet at ~1:51 minutes into the video.