Wireless home internet

I've got my PC plugged into the wireless router.
Overnight, I might get 30Mbps for a short time. The rest of the time its 3Mbps or slower.
Here, at 5PM, I can barely load a single web page... no other devices using internet.

My providor is Softbank and I feel royally screwed by them. It's like 6000 Yen/month and the internet sucks SO HARD.
The stores have awful customer service. Shocking in Japan! Rude and they don't care AT ALL. I have money and I need wireless internet. But I don't know what to expect with the competition. Sure, my 4G is 20-40Mbps but that's expensive and limited. I play games, download software and chat.

Any ideas?

introduce optical fiber cable into your home. (usually NTT)
take a good provider. (some providers put many customers to a narrow band-width. so always busy.)
Lan cable works always better than wireless. use a high fidelity (efficiency) router.
ask your friends who know more.

true Softbank is not the most suitable player for the internet.

I have NTT (=docomo) at home (optical) which is perfect for me.
Wireless one three floors of the house and never have a drop out.