Help with Apple wifi setup

My wifi setup is ****ed, looking to the mcbrawl community because the apple tech nerds were useless.
heres what it looks like
theres the main house and the back house where my parents work
in the back house is where we have the router and the airport base station
the router is plugged into the base station via ethernet cable
there are two ethernet cables connected to the base station
one connects straight to my mom's imac, she gets 80 mbps fromit
one runs into the house, and when i connect my laptop to that one i get 80 mbps

so we know the base station, router, and both ethernet cables are working

to extend the network (because the setup is so spread out) we have an airport express in the main house that connects to the second ethernet cable
but recently, that setup stopped working
after lots of troubleshooting i found that i would get connection if i removed the ethernet from the airport express
my ping was low, but since the signal from the base station was weak at that range, i got 3 mbps
when i plug in the ethernet cable, which connects straight to the base station, **** breaks again
my ping times out every time
so my question is simple

how do i fix it

 

Nevermind, solved
thanks internet