Run the Apple Diagnostics.
Maybe the liquid spill and the slowness are two different things. You can run EtreCheck to look for possible software issues for the slowness. Feel free to post the EtreCheck report here using the "Additional Text" icon which looks like a piece of paper.
If your laptop has a hard drive, then perhaps it is beginning to fail. Both the Apple Diagnostics and EtreCheck may be able to detect some hard drive failures, but if they don't show a drive failure, then a better app for checking a hard drive's health is DriveDX. Feel free to post the report here using the "Additional Text" icon which looks like a piece of paper.
Of course liquid damage can sometimes cause affect system performance.