Unfortunately you are hitting on the one true drawback when building software which is the time it takes. Still starting with the kernel and extending to most of the packages I would argue (others can help to support the fact) that software built locally or for the specs you tell it to use will perform better on your machine with significant improvements for the system, such as less application crashes and a more stable and probably faster experience if you optimize everything in that way.
does gentoo have an option to use other command than "emerge" like "apt-get" to download and install binary packages like in debian?
Still the answer is it is possible and you would want to use emerge flag —install for something like that i believe. But how you will make sure all the dependencies are met in that case is basically also why doing so could have some unexpected results such as other packages being unsble to use the software for dependency or just having to learn a bit more too about ebuilds.
There are other distros with packagd managers geared more towards working with prebuilt binaries, Debian, Slackware and Arch linux tonname a few.
hey so if you plan to stick with it in Gentoo, including:
1. Holding back certain package upgrades, with package masks will help you control when you want to rebuild a package, which can help for those longer builds like the browsers or huge gui applications which i would agree there is little parience involved in waiting for that to get done
2. Also search the tree for binary packages (qsearch -s ‘-bin’, with portageq installed first) when it looks like the package could take a while, to build
3. Use cron jobs or another way of scheduling your updates so that they do not interfere(overnight maybe
4. Lastly make sure you use —ask or —pretend flag with emerge and read over the list of changes that will happen before continuing you updates so that you can ensure that all software or changes to system software really needs to be there.