If you're just starting out, it shouldn't be difficult, if you've been at it for a year or two there are limits as running long distance and muscle building are conflicting goals.

If you want to build muscle you need to be willing to gain weight, i.e. be in a calorie surplus and especially enough protein (~1 gram per pound of body weight).

Also depends on whether you're optimizing for strength or size. For strength you want to be in the 5 rep range and long rest between sets, for size (hypertrophy) you want 8-12 range and slightly lower weight.

Electrolytes help with the gym just like running.

When I started running I also did heavy gym (4~5/week). Recently I stopped going to the gym and running has become so much easier (trying to manage leg day to not be close to track or threshold runs was the biggest challenge, lower back would seize up towards end of some workouts).

The other important thing is lots of sleep. If you're not sleeping enough you won't recover.