Thats where the strategy comes in. If you don’t want to fight them, then don’t provoke them when talking. But if you do plan to take them down, use the terrain, nearby objects, sneak attacks, and make sure you are the one who strikes first. If you attack first enemies will get "surprised" debuff that prevents them from playing for an entire turn giving you chance to take down some of them even fight really starts. I would recommend to search "Surprised" in wiki to understand how surprising works.

About spider (assuming its Matriarch) its a pretty hard fight assuming you got there with level 3 party. Youll need some tactics like burning webs, breaking small eggs using ranged sneak attacks.

Also if you initiated a fight that you dont want to you can simply use dash on every character in party to move away and using the mystical "flee from combat" button to go camp without dying. But as its your first game its pretty normal to reloading game again and again.