“L5-S1…moderate lateral recess stenosis and neural forminal narrowing on the left with impingement on the l5 and s1 nerve roots on the left…L4-l5 4 to 5 mm left paracentral disc protrusion with moderate neural foraminal narrowing bilaterally with indentation on l4 nerve root greater on the left than right”.
It appears that you have a herniated disc, lateral recess stenosis and foraminal stenosis on the left at L4-5 and L5-S1. This problem becomes more symptomatic when you stand as the nerve hole narrows when you stand. See these hyperlinks to understand:
https://neckandback.com/conditions/foraminal-collapse-lumbar-spine/
https://neckandback.com/conditions/lateral-recess-stenosis/
https://neckandback.com/conditions/herniated-disc-lumbar-spine/
You more likely need a surgical workup which consists of diagnostic blocks and possibly surgery.
Dr. Corenman