If other devices also have problem it may be caused by router, other networks or your ISP provider. If not then it may be caused by:
- IPv6 – disable
- MAC randomization –disable
- Bluetooth – disable
- bad connection caused by long distance, obstacles and other physical things – pull router out of cabinet and/or move computer into its neighborhood
- bad connection caused by other networks – change channels
- outdated BIOS version – update
- construction error or broken Wi-Fi card – you do nothing
- other things which I don’t know.