I have installed the range extender successfully.
For reference, the set up is as follows
Main Wifi: SIDD12345
Password: <same as Main wifi>
I have to add SIDD12345_EXT under my Wifi networks on mobile/Laptop as a separate network. Due to this, most of the time, I lose the internet because the device tries to jump between the networks (week signal main network and strong ext network) when I am going around. And most of the time I do not even get connected to the internet when I am connected to the extended networks. I see a good signal on the extender though.
Can it be possible to not to have range extender its own wifi and just boost the main wifi so that I can use only the main wifi credentials?