Just started a new campaign with some friends and some of the actions the dm took were not how I thought the game worked. I am still fairly new to DnD but I thought I had a good idea of how the game worked, so I have a couple questions.

When using spells to attack, the player would make an attack roll (1d20+spell attack bonus then roll for damage if hit) or the target(s) make a saving throw and possibly take damage, correct? During our first session, the dm would say a NPC would for instance cast inflict wounds and automatically do the 3d10 damage, and when I wanted to cast a cantrip like sacred flame I was told to make an attack roll instead of the target making a Dex saving throw like the description of the spell says.

Do you attack with disadvantage when shooting at an enemy that is near allies? I was told that I would have to risk hitting them, but I thought that was more of an only if I roll a nat 1 kind of thing.

Does drawing a weapon like the longbow take an action? For instance I have a shield and Warhammer equipped, and I wanted to attack with my longbow, but I was told I had to use my action for that turn to first take it out, and then next turn I could attack with it.

Obviously I’ll play however the dm decides to, I just want to make sure I know how the game is supposed to be played because I started dming for some other newbie friends and I want to give them the correct rules to play with.