RTOSes are developed to solve this exact problem of concurrency. Try Zephyr, ThreadX (from MS) or FreeRTOS (from Amazon) or whichever OS your microcontroller vendor supports. It will be eye opening, and you get to learn to write safe code in C with synchronization primitives just like our ancestors.
Amazon did not create FreeRTOS; they simply took over maintenance a few years back. I didn’t know that happened until I fact-checked your comment, but it is enough to make me never want to use it ever again. And that makes me very sad.
They improved the licensing to MIT. The pre-acquisition license was "GPL" but it had a noncompliant restriction prohibiting comparative benchmarks. There have also been useful improvements to the codebase. Amazon is a net positive in this case.
