For the mines there are a few things that could help you.
For Elliot just by the beach. He's normally on the beach or staring at the river on the bridge.
For the travel cart any items you've missed in bundles, rare seeds or animal products (duck feather or rabbit's foot). it gets easier.
For fishing, the mountain and town are best places to fish. Don't worry it gets easier over time.
Chests are fine in front of the house. You can get a storehouse after just don't let it block any building projects.
For energy you can make a foraging bar or visit the Spa in Summer. You can also talk to villagers or try killing enemies in the mine for items.