Here in your major explanation you have told you have problem with your left shoulder and arm along with range restriction.
Here your problem could be related to 4 things,
1. It can be
frozen shoulder.
2. It can be
soft tissue (
rotator cuff ) damage covering your shoulder joint.
3. It can be some thing related to heart problem.
4. Shoulder joint osteo
arthritis.
Now if you see you have pain while lifting hand up and resisting movement and not allowing any movement. That means only with
muscle contraction ( tightening ) if pain is present then it is soft tissue pain.
If there is no pain while lifting hand up and resisting movement. But there is pain when movement is allowed. That means pain while moving the joint then it is frozen shoulder.
If you feel pain in chest along with breathing difficulty while walking up hill or running or jogging then it can be due to heart weakness and heart related issues.
Here whatever is your condition the conformation between frozen shoulder and soft tissue damage can be done by MRI of shoulder as well with ortho and physio specialist examination too.
Now based on that there will be treatment given. For severe damage in shoulder joint there will be arthro scopy repair can be done. And if joint is deform due to osteo arthritis then
shoulder replacement has to be done.
And if there is mild to moderate problem then you will be fine with
physiotherapy treatment and exercises.
You can also use hot pack on your shoulder for some more pain relief.
Now if there is problem with heart then your doctor will ask you to do ECG and tredmile test and based on that there will be treatment plan. It can be medical or surgical again.
Here also in the end physio therapy will help for getting you back to normal life.
Take care.