Fishing is impossible

[Quirinea]

If you can use mods, there are a lot that make fishing easier. They were the saviour for me. I usually put the difficulty to something around 25 to 35 of "normal" and ta-dah, it is meditative and fun. At least some of them can be set to remove the minigame completely (if you have e.g. issues with your hands).
If you will not or cannot use mods, then there is a way to slowly get the fishing level up (and the bar larger): The catch from crab pots gives you experience points. You get three of them from the crab pot bundle, and you can get four items by foraging, the last one from the mines. Then be kind to Linus and he teaches you his bait recipe, which does not require a fishing level.

Another way to raise fishing level without the minigame: fish trash. Farm pond in standard farm, mines, Desert pond after 8 PM.

 

[PoppyForPenny]

I had a hard time learning to fish. There is a rhythm to it, controlling the bar is like, taptap taaap, taptaptap, taaap. Gentle, tiny. Foods to boost, and leveling up really help. Carp are easy from the mountain lake, sometimes they just stay right at the bottom so you don't have to do anything. And catching trash does level you up! I encourage you to keep trying, a little bit here & there! It's so rewarding to complete the community center and you can take all the time you want.

 

[nicodeux]

Like many here, I had a hard time learning how to fish in the game. I even believed at a time that fishing was broken on mobile before realising that this is just significantly harder than other professions in Stardew Valley.

If this can help, you can look at videos from players to see how the fishing mini-game is supposed to be played and then try to mimick those moves.