Well assuming you have clearance to use their wifi in the 1st place you or they could buy wifi repeaters & that should help, depending on where they are placed & where you are to the connection.
If you are just trying to boost a connection without their knowledge or access then that's not going to happen.
Sharing an Internet connection with a neighbour can be risky. Any malware or virus infections on devices in one household could spread to devices in the other household. Computers can be at increased risk of hacking from the neighbours. If any crime is committed online by your neighbour it may be very difficult to prove it wasn't you who did the hacking.
Also, in some countries or states sharing an ISP connection between households is illegal.
If you plan to use your neighbour's network without their permission and agreement, then you are committing theft and can be prosecuted and end up with a criminal record.
I strongly recommend that you get your own ISP connection or use a cellular Internet service.
You'd tell them to buy and install a wifi booster.
Good luck with that.
You cant use their wifi without their permission – that would be stealing.
So you want to steal their internet?