What should I do if my internet connection is normal during the day but becomes incredibly slow and unresponsive at night after returning to China?

Overseas students and Chinese using VPNs to access services back to China often encounter a problem: It works perfectly during the day—smooth video streaming, low latency gaming, and clear video calls. But at night, the situation drastically changes. Videos load in a blur, game latency spikes to 200ms+, video calls become pixelated, and the entire experience becomes choppy…