I had this problem too.
The issue for me was that my computer had two disks, a small fast one (sata ssd) and a large slow one. Windows had separated itself with the operating system itself and installed programs on the ssd, with all user documents on the slow disk.
Linux can do this too. Put a partition mounted on / (root) on the fast disk, and one mounted on /home on the large disk.
I’d put both on the large disc initially.
There’s a part of the installation where you set up the partitioning. Redoing the installation really sped up my Linux Mint installation.
It seems unlikely that downgrading to 32 bit would substantially change anything. I think it means to downgrade specifically if you want to report a bug. I don’t often use Lutris though, so I’m not sure.
Maybe you need to update your package manager?