Tail lights

Never use a larger amperage fuse to repair a problem. It could cause the wiring to melt down a then catch fire.

You have a direct short. The signals and brake lights work a from different power source. I would start by checking the light sockets them self. Does the fuse blow when there is no light bulb installed? If not, see if there is power to the wiring at the socket. If there is, then the socket is bad. If the fuse blows when there are no bulbs in place, the short is before the bulb. At that point, you need to trace the wiring to locate the problem area.