To optimize the downloading time, you can edit following variable for saving the packages in a separate place :
DL_DIR ?= "${BSPDIR}/../yocto_dl/v5.10"
Once downloaded, next bitbaking will take less time and avoid issue with the network. Also, packages can also be shared for different working bsp folders to save disk space.
The build process is long, also the same in our side, it is related by the network and your PC performance.