>>76745393
>Mobility
No idea sorry, but there are a few stretches which are pretty good for runners like "the world's greatest stretch".

>Strength
Pick your favourite out of Starting Strength, Greyskull LP, and Stronglifts 5x5. The first two have books, the third has a website. They're all very similar, and are based around low volume with big compound exercises (squat, deadlift). You might want to supplement it with calf raises, especially seated.

It's important to and to add weight every single session. So even if you start with just the barbell, it will get very hard very quickly. So in order to recover, you might want to wind your running back a bit while you focus on strength for a few months. Once you've built it up, maintenance is much easier. Picrel is a variant of Greyskull which is more upper-body focused, so it probably doesn't make that much sense for a runner. I'd say Stronglifts 5x5 might be your best bet. It even has a pretty decent app which tells you exactly what to do.

Also remember to eat enough protein, get enough sleep, and try to be in a caloric surplus. As you add weight, remember to regularly review technique guides online. They won't help much in your first session, but they will make more sense the more you develop in your own abilities.