Severe back pain, sometimes restricts my movement highly

I’m sorry for all you have been through and continue to experience.

Do your symptoms improve when you bend forward? Dipo you tend to walk bent over or feel less pain this way (flexion)? Is your pain with walking all back pain or do u experience leg pain, heaviness in legs? Does your pain radiate to non-back areas like the buttocks, thighs, or hips? Do u experience any numbness, pins and needles, or leg weakness?
Any balance issues? Have you tried riding a stationary bicycle? Does that exacerbate your pain?

You mention moderate to severe stenosis. Does it mention a particular millimeter? Is nerve impingement noted in the MRI report?

Do you have any history of blood vessel disease like heart attack, stroke? Has any doctors ever told you your pulses in your feet were diminished?

meysodose, sorry it took so long for you to finally get imaging.
Luckily, your trouble is limited to two levels and you are at grade one which is 1 to 25% slippage. Usually spondylolisthesis (vertebra slipping) L4 vertebra is slipping forward over L5 reducing the space for the spinal cord and reducing the space at the sides of the vertebra where nerves exit.
This usually happens because of a fracture or because the disc between the vertebra is compressed and bulging into the canal space. When you bend forward that space opens up and when you are upright the space narrows.
There are procedures and surgeries that can alleviate the pain.
The first you might try is fact joint injection. Under fluoroscopy a doctor can inject steroid and reduce inflammation that presses on exiting nerves. Some people get these injections several times a year and have sufficient relief. If the injections help initially you could have radiofrequency to the medial branch nerve that carries pain signals to the brain.
You also have reduced space in the central canal. And may need that addressed to happily maintain the upright position. You might have surgery to reduce the size of the ligament at that level. You might have micro discectomy to remove the protruding portion of the disc. You could have the disc removed and have L4-5 fused or have the disc removed and an artificial disc inserted.
Laura1970's questions lead to answers about what procedures would help the most.
I hope you find relief.
https://www.osteofisioluciani.com/en/blog/spondylolisthesis-physiotherapy-rome

I am similar. My back pain started about 6 years ago. Arthritis caused my lower spine to curve with disc displacement. It was painful to walk, lift or exercise.
I started with steroid shots in the L3-L5 with a pain med doctor. They worked pretty good and lasted about 10 months. I than had the same series of shots for 4 years.
My last MRI showed severe curved spine with disc degeneration. I did a series of steroid shots but they did not work very well. I visited a surgeon and he suggested surgery with pins plus some other things to straighten out the spine and that should relieve most of my pain. Just before the surgery, I came down with cancer. The surgeon said he cannot do that surgery due to the cancer and I had to postpone at least a 6 months to a year after all treatments and cleared of cancer. I finished cancer treatments in Dec and just waiting on follow up with the oncologist. So I still cannot do the surgery
Right now I am in severe pain cannot walk much either. I went back to my pain med doctor and he suggest a treatment called Intracept. This heats the vein to stop sending pain signals to the brain. It is a bit more invasive but still can be done as out-patient. I scheduled this for the end of Jan.