do i need a external antenna

i’m a new user to the 5g home internet i’m running about 120 mbps for upload and 10 downloads and running about three bars on the router and was curious if i should invest into one of the external antennas or if i should try to get a different router i have to put the router in my garage to get this if it’s in the house i can’t it’s 1 to 2 bars or no signal at all.