I use a really handy app on my phone, "Film Developer Pro" which cost something silly like 3 dollarpounds. You can select your film size, film brand/type, developer, ISO speed you shot at (for push and pull), and temperature of your chemicals for pretty much any feasible B&W film/developer combo. And you can select how often you agitate, and for how long. The app will then give you a recommended development time and has a countdown timer built in with audible pips to fill the tank, to agitate and to end your process and empty the tank.
+1 on not starting with stand or semi stand development. I know some folk swear by it but in something nearly 40 years of developing film I've never even felt a need to try. The easiest place to try is with a common film and developer combo, shoot at box speed and follow the film manufacturer's instructions. You can then learn with your first few rolls if you need to tweak your technique. But, barring some unforeseen disaster, you'll get decent results keeping it simple to begin with. Then later have fun with different developers, try stand and semi stand if you like, try pushing and pulling, experiment with different films and then try colour. I've not done C41 but I have done E6 and it's not *that* much more difficult than B&W, the main thing is maintaining a consistent temperature within 0.5C of the standard.
Temperature isn't as vital for B&W as it is with colour but it's not unimportant especially if your room temperature (and thus likely your developer itself) is more than 2C either side of 20C. That's where the app I mentioned can come in handy. Temperature can also affect the contrast of the negatives and you do want to try to avoid development times under 6 minutes if possible.....that way the small deviations in time spent pouring in and out really don't matter.