Newly adopted shelter dog is very skittish, wont even step foot outside my apartment door, and wont potty in front of me

I recently just adopted a new dog (two days ago) and am a first-time owner (at least by myself, I had a childhood dog but parents took care mostly). I know very little about her history but that the shelter told me she was very skittish and likely will take very long to decompress and I want to prepare for that.

She has only stayed mostly in her crate. When I go to my room, she will come out of the crate to sniff around and go back in when I return. She will come out when I put the food bowl out front and she'll stay around since I will start throwing treats to get her accustomed to me being in the room. She surprising takes medication well; I have to put some ear cleanser on her daily and she handled it well and I rewarded her with treats after.

I attempted to take her outside to potty and see if she was potty-trained, but she absolutely did not want to go outside and I had to carry her down the elevator. Eventually, she was pulling on the leash to go back so I brought her back upstairs and she pooped in the hallway ;-; She absolutely avoids the front door and will back away if I open the door at all. She has also started backing away when I walk into the living room (where her crate is) since that incident.

I have puppy pads out now since I think it's probably too much stress bringing her outside and she likely lost trust in me for doing that but now she's just laying on the puppy pads so I took them away! I know it's only been two days but this is my first time taking care of a dog, a shelter dog too, and I'm worried about setting things off on the wrong foot. For the time being, I've just stay around her during meal times for about 30 or so minutes then leaving to my room so she can have privacy and go potty and explore the apartment some more but I fear I might be normalizing this behavior.

I understand the basics of taking her out often for housetraining but if she's very skittish of me, I feel that carrying her out would only further ruin the trust building and keep resetting us back to square one. I don't want her to develop bad habits in the house and I also want to make sure she gets a good quality of life. I'm worried she won't get the enrichment/excitement she needs if she's just cooped up in the apartment all the time too.