4 questions regarding database

There are 4 questions that need to be explained.Please look for the attached files.Let me know if you have any questions.
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err_3_44.pdf

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EVENT
MANAGER
PK
Manager ID
Name
PK
Event ID
FK
Organiser ID
FK
Artist ID
Location
Date
Assistant Name
Country
Location
Cancelled
ARTIST
Artist
PK
Artist ID
Name
Music Type
FK
Manager ID
Gender
SOURCE OF
RECOMMENDATION
PK
FK
PROSPECTIVE ARTIST
MUSIC SAMPLES
Recommendation
ID
PK
FK
PK
Address
Artist ID
email
Source File
Music File
Name
honors
Source Reference
Music File
Artist ID
INSTRUMENT
PLAYED
Phone Number
Music Sample
ID
ID
Artist ID
Instrument
Name
University Degree
Year of Birth
University Degrees
Source of
Recommendation
Organiser
PK
CONTRACT
Organiser ID
Organiser Name
PK
Contract ID
FK
Artist ID
BILLING
PK
Billing ID
Event ID
Signed Date
Location
Billing Date
Royalty
Tax
Artist Fee
ARTIST EXPENSE
MANAGER EXPENSE
PK
FK
Manager Expense ID
PK
Event ID
FK
Expenses
Artist Expense ID
ARTIST
SCHEDULING
PK
Schedule ID
Event ID
Priority Level
Expenses
Date
…
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