please see the usage of linking verbs

[jahangir]

I have problem in using linking verbs. Please correct my sentence if so.

The Key shall be on the table
I will be there
I can’t be there because I have to go .
I should be in office within 5 minutes.
i would be there after 5 minutes.
The pigeon has been on the wall in morning.
I have been in London
The money had been in table desk before I left from house.
As for now, I shall have been there
Anyone of them could have been in Sardinia at the time of jeep accident.

I wish I shall be a doctor.
After one year I will be graduate
I can’t be a doctor because I doing commerce.
I should be a good Accountant.
I would be a senior Accountant by 2007
My brother has been sale executive for 2 year
I have been a customer service representative for while
My father had been weight lifter in college.
As for now, I shall have been a Engineer I couldn’t failed in exam
Any one of us couldn’t have been a player in our college.

[Mariner]

It's all about what kind of meaning you want to convey. Examples:

The Key shall be on the table would probably sound less formal/authoritative if you would use will instead of shall.

I presume that with I would be there after 5 minutes you meant to say I will be there after 5 minutes

The pigeon has been on the wall in morning. Even if you put the missing article before morning, the phrase is still ungrammatical. You use past tense when you refer to a definite point in the past. So, either The pigeon has been on the wall or, alternatively, The pigeon was on the wall in the morning

For the same reasons: The money was on the table desk when I left the house. Generally speaking, I believe this is where you should focus on. Quite a few of your sentences had this past simple/past perfect mistake.
As for now, I shall have been there. I'm not sure what you meant to say by that.

I wish I were a doctor. Or, I wish to become a doctor


You do have some correct ones, too,
I will be there
I have been in London
I should be a good [a]ccountant (grammatical; correct if you meant to say that you should be a good accountant, yet you are not)