2 LAN 2 WAN each using different ISP with load balancing and failover

RouterOS Beginner Basics
1

My setup is

int1 - 210.4.73.114/24 wan1
int2 - 192.168.0.1/24 lan1
int3 - 202.51.183.54/24 wan2
int4 - 192.168.200.1/24 lan2

what i want is

  1. LAN1 to use WAN1 and LAN2 to use WAN2
  2. LAN1 and LAN2 communicate easily
  3. Loadbalancing and failover configuration

please help me out here cause i am new in routeros environment. please specify how to configure NAT,firewall,mangle etc.