Esp32 & sd card HELP!

I am developing an ESP32-based cloud storage with an SD card module. In fact, ESP32 hosts a web interface through which you can upload, download, view and manage files. But then I ran into a problem — the download speed limit. At the moment, the maximum that could be squeezed out is 100-200 kB/s, and even this speed drops after 5-10 seconds.(I used a buffer) I am looking for solutions to transfer files stably and quickly. What advice can you give on optimizing speed and in general on approaches for such tasks?