Orange tree

[Hana]

Hi everyone,
I bought an orange tree about 5ft high from a nersery when it was in a bad shape and I mean yellowing. All of the new sets of sprigs were yellow. They told me it was new growth but nope, I noticed empty stems at the top among the yellow sprigs that're about a foot in height. Been keeping it indoors since I brought it in about 2 weeks ago in a bright, cool corner where it's 82 °F. It took 4 days to dry out before I neely watered thoroughly as the upper leaves showed signs of wilt. I haven't transplanted it yet but changed the first 3 inches of soil using potting soil. I tried to fertilize it too with coffee grounds and kitchen scraps infusions .. no change!!  It's condition is worsening for it's yellowing almost all over and as it's been losing leaves ever since I brought it indoors. I will show some images hoping to succeed in posting them for I'm new to this.
Any feedback will be greatly appreciated. Thank you in advance.
Ps: I'm keeping it in a container for growing in a balcony. Brought it indoors for shelter from the scorching heat. It's three digits in my region pretty dry and sometimes windy too.

[luak]

Big tree, little pot not good, possible root problem. When going to a bigger pot do not fertilize yet,just water with a p/h of about 6 or 6.5. Keep in shade.

[Millet]

Coffee and kitchen scraps are no fertilizer for a citrus tree.  Luak, is correct, the container is too small for a 5-ft. tree.  The medium the tree is now growing in is not free draining enough. Straight potting soil is also not a good medium for the tree.  I would pull the tree out of the container, remove as much of the soil as possible, (flushing with water), avoid damaging the roots.  Replace with a faster draining mixture.  In the future use a real fertilizer that is higher in nitrogen and potassium, and lower is phosphorous. Good luck to you and this tree.