Best way to protect yourself from malware and payloads on a public wifi

I have to use the public Wi-Fi network, because I'm traveling. Using Linux, with an updated kernel. Currently, the BIOS and firmware are not being corrected, which may be the cause of my malware attack. It was not too serious (my paper was changed, etc.)

I try to understand how I can avoid data payloads when I call public wifis password-protected, the mechanism behind it.

One of my thoughts was to use a password-protected Rasberry pi VPN router. Is this what you're going to do or are there better ways to protect yourself in public Wi-Fi?