I'm playing my first D&D 5e character, a Wood Elf Fighter with the Soldier background. I have proficiency in the skills Acrobatics and Survival from the Fighter class, and Athletics and Intimidation from the Soldier background
I've just reached level 5, so my proficiency bonus increases from +2 to +3.
It makes sense that this bonus increase applies to my Fighter skills, since my level as a Fighter has increased, but do I also increase the proficiency in the two background skills?
Best Answer
Yes.
Proficiency isn't tied to anything except your character level (i.e if you multiclass for example Rogue 3 / Cleric 2, your character level is 5, which means your proficiency bonus is +3).
Your proficiency bonus increases everything you're proficient in, full stop. This applies to attacks with weapons you're proficient with, saving throws you're proficient in, skills you're proficient in, etc.
From the Basic Rules, p. 7: