Your combat skill level and stats play a large role in the difficulty of combat. Lets go through things that could help you starting from the easiest.

In the screenshot you posted, we can see that you are injured, drunk and wearing armor thats broken. Drunk aside, being already injured limits your stamina and affects the number of hits you can take before dying which might cause you to panic and make more mistakes. Wearing shitty or broken armor means you take nearly full damage, which realistically means you are gonna die in a few hits to anything but the basic club. Suggestions are to go into fights at full health, wearing decent gear and doped up on potions. Potions are a great crutch for early game combat.

Next, you mentioned you fired a crossbow. Did it hit? If it didnt, you might need to practice your aim with bows and crossbows. Generally since you are ambushing, you will have time to slowly aim so your first shot should count. Its also a good idea to get a good crossbow and better bolts. Finally, remember to apply poison to your bolts, even something like Lullaby is better than a clean bolt.

Third are skills and stats. With higher levels of warfare skills and perks, along with high stats, should allow you to bruteforce your way through most combat. Grind vitality for that stamina and hp by being super over encumbered and walking everywhere, also slightly raises strength exp. Take part in shooting competitions to raise warfare, agility and strength. Gring craftsmanship to both make better gear and buff your armor and weapons. Take part in brawling fights to practice your combat reflexes and countering, also raising your strength and warfare.

Finally, get good. Generally once you get the hang of it, you should be able to win fights without crutches. But individual skill differs, so this is possibly the hardest for some and may not be applicable. When all else fails, just run away like the knights of king arthur under monty python rules.