I've only used it for light editing of Word and Excel files and never noticed any "slowdowns" on a Snapdragon 845 with 3GB RAM.
For any real usage, I recommend using the Online app or Full desktop app for a better view and full keyboard/typing access.
Slowdown may be caused by aging hardware, not enough memory, software problems, incompatibilities etc. Troubleshooting is suggested, but if the device is old then upgrade is advisable.
You can pick up a new mid-range Android from around $400+.
Keep an Android phone for 3-4 years, or iPhones for 4-5 years.