If your Mac SSD is slow then you need to check the health of the SSD. There are different models of the Mac that comes with SSD and HDD both. If your Mac has only using SSD, then you must keep an eye on the health of the SSD because it has age and if the lifespan comes to an end, you might fail to write data on the drive.
Check SSD Health through System Information
Click the Apple menu in the menu bar and select About this Mac. In the window that opens, go to the Overview tab, and click the System Report button. In the System Report window, select Storage in the column on the left. This will show you the current status of the SSD on your Mac.
Check SSD Health thorough Chameleon
Chameleon is a free and useful app provides accurate health status of the SSD. Moreover, it also provides support for disabling/enable TRIM i.e. the SSD is not from Apple but it is just information and has nothing to mess with.
You can download Chameleon from here.
Check SSD Health using Blackmagic Disk Speed Test
The Blackmagic Disk Speed Test is for testing the SSD. The application executes a stress test that can test the performance of the SSD. It will provide a complete read and write details and allows the users to check the speed of the SSD.
All it needs is to start the test from the start button and watch the results. If the SSD test fails, then you must change it before anything goes wrong.
You can download the Blackmagic Speed Test from here.
If you are using an SSD drive then you need to maintain a backup of the data.