My PC is wired connected to my router (running OpenWRT 15.05), it gets the following range to its IP: 192.168.1.x and my Android Phone connected trhough WiFi to this same router but he receives the 192.168.0.x range... I can't share files trough samba server (windows) to my Phone (I guess it's because they're in different network ranges) and I don't have much time to use the computer. How can I set WLAN network to be the same as LAN network? Or maybe use NAT to connect them (even if the devices are connected trough different networks)?

Please help, I've made a lot of search and didn't find anything relevant...

Thanks in advance.

Configure it as a "dumb AP", there is a guide.

By default they should be in the same network, lan. 

On the network - interfaces page, you should have two networks wan and lan.  Check the physical settings of each one.  The wan should only be connected to your ISP.  The lan should have both the ethernet ports and the wifi.

The most likely way for the problem you describe to occur is if one of the devices is actually going directly to the modem/router instead of the OpenWrt router.