Man I must just suck at this game. I'm horrible and it's getting a little frustrating. The tests of strengths are brutal for me, i'm about 4-5 hours in around the Zora area and the stupid thing kills me in a few shots. I'm terrible with the bow, i'm pressing all the wrong buttons when I try to throw bombs in the middle of combats, all my weapons are breaking, and I don't even think I faced a real boss yet so I have no idea how I'm going to manage that. Locking onto enimies and trying to use the shield feels like it barely works and don't even get me started with the stupid thing that come out of the water and continuously hits me with coconuts or whatever they are...
Couple things:
1. Practice dodging left/right or back whenever the enemy is about to perform an attack. If you time it right, you get a "flurry rush" which gives you a ton of free hits on the opponent. It is incredibly intuitive, so once you start getting the hang of it the action should come naturally. This is incredibly important for tests of strength (and is actually a good tutorial for that because the guardian scouts telegraph the time and direction of their attacks)
2. When you encounter the octoroks (the enemy that shoots coconuts at you), if you shoot/hit the plant on their head, they will pop out and you can easily kill them. But yes, very annoying to deal with.
3. At some point you are going to encounter actual guardians (the big machines that are littered across the map, whether living or dead). They will lock on to your player and at a certain point will fire a very devastating beam at you. If you are able to parry (press A) at the right time you will be able to reflect it back on the guardian and either severely damage it or destroy it outright (and these drop very valuable loot).
4. One of the first places you should try to get to is Faron Tower (southeast area of the map):
Just north of the tower is a small forest where the trees drop "hearty durians". If you cook a single hearty durian with any one food (an apple for example) it will completely restore your health and add four extra hearts. Every hearty durian you add to a meal adds an additional four hearts. A great resource in the early game when you don't have a lot of hearts, yet.
5. At the end of the day, keep practicing and be patient. Once you get the hang of the timing of dodging/attacking then a lot of the fights will be much easier. Same thing with the bow and abilities.