is working in investment banking is halal their work is related to merger and acquisition, manage client portfolio, act as a intermediate between compony and commercial bank (they advice bank to issue Loan to compony or not they also help compony in issue a share

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

The ruling on the type of work in the field that you mentioned depends on the type of work: if a person deals with forbidden work or helps in it, then it is not permissible for him to work in such a job because Allah Says (what means): {but do not cooperate in sin and transgression.} [Quran 5:2]

If the work is free from this, then there is no harm for a person to do this kind of work.

Thus, if the banks that mediate between the employee and the companies to grant loans are Riba-based banks, then it is not permissible to act as a mediator between them, either in granting loans or doing any other prohibited transactions.

With regard to assisting companies in issuing shares, what has to be looked at is the activity of the company: if it is forbidden, it is not permissible to help it in issuing shares; the same thing applies if they deal with Riba (interest and/or usury) when lending or borrowing, as it is not permissible to buy their shares.

Therefore, the issue is as explained above and a person has to be aware of what he wants to do about that. He should know that the means of lawful earnings are so many for those who seek them and that there is no good, nor blessing, nor abundance in what is forbidden.

A person should be concerned about how to earn lawful earnings and how to fear his Lord.

Zayd ibn Thabit narrated that the Prophet said: “Whoever makes the Hereafter his goal, Allah makes his heart rich, and organizes his affairs, and the world comes to him whether it wants to or not. And whoever makes the world his goal, Allah puts his poverty right before his eyes, and disorganizes his affairs, and the world does not come to him, except what has been decreed for him." [Ahmad, Ibn Majah, Ad-Darimi, Ibn Hibban, and al-Bayhaqi]

Al-'Iraqi said in Takhreej al-Ihyaa’: “It was reported by Ibn Majah and narrated by Zayd ibn Thabit, and Shaykh al-Albani classified it as Saheeh (authentic) in Silsilatul-Ahadeeth as-Saheehah”

Allah knows best.