Helps to make code faster

Dear all,

I have written code to calculate a usage of an item and other calculation. If I copy my code to a word file it will become 19 pages.
I am running this code and it takes 45 minutes before I end it.

The code is checking a data having an excess of 150000 rows.

Is there anyone kindly enough to walkthrough my code and give me suggestion to make it shorter and faster? (I have attached the file)
I made this code based on little knowledge of VBA.

Secondly is there any relation having a macro running on a large file (>10 MB) with its speed?

Thanks in advance