how can I sue Google and Apple for not letting me change my device’s MAC address (Pixel and iPhone) and internet companies for leaking my IP addresses for tracking my internet activity or to track me. Does it violate GDPR requirements?

For changing your MAC address, randomly generated MAC addresses are the norm unless you change your settings to use a static one. You can set up your phone to use the phone's MAC or to generate a new one every time, but by default it'll generate a MAC address per WiFi network.

As for tracking you and your internet activity, you can file a complaint with your local DPA to hopefully spur them into action, that's free. If they don't take action, or decide that your complaint won't convince a judge, you can contact a legal professional and pay them to take your case to court like with any other legal matter.

What are you talking about? Both iPhones and Android let you spoof your MAC address to a random or fixed value if you want, for privacy.

Also, "leaking my IP addresses" how the fuck do you expect a website to talk to you without an IP address to send the data back to.