GST ON CONSULTANCY SERVICE TO FOREIGN COMPNAY

Our client an individual was recently took up an assignment (Site supervision of ship building in Indian yards - Goa in India) for a German company. German company is in the process of ship building under "Make In India project" in India. After completion ships shall be taken to their country. Terms of agreement includes monthly professional charges shall be paid in US$ 5,000 per month (deduction of 25 US$) on account of tax (VAT). Travelling and other expenses in relation to movement within Indian yards to be paid separately. Initial contract for 6 ship building (3 years) subject to renewal on satisfactory completion of first term. Agreement has to be renewed once in 11 months. My client has received two months pay in convertible foreign exchange (US$) and credited to his local bank account. German company needs an invoice (need not be Tax Invoice) for the purpose of paying his professional fees. My query for experts are

(a) Should he get registration under GST..?

(b) Is the professional service an "export service" in this case ?

(c) If he has to get registration under GST law, what is the rate of tax..?

[He is giving his service in India for a foreign company and receiving his fees in US$ into his local bank account].

Thank you