Tax returns for a partnership that controls a foreign company

A client formed a general partnership in California and used the capital to found a startup company overseas. The partnership has the control of the foreign company.

I understand that a partnership return is needed and form 5741 will be filed with 1065. Since I have never done a return like this, could the community help out with the steps/information I might need? They don’t have a book for the partnership as the transactions are simple money in (partners’ contributions) and money out (wire out money to the company they founded). I have the partnership bank statements and will ask for the income statement and balance sheet for the company. Anything else that I need?

Also, one partner is a foreigner with no SSN/TIN so I will need to file W-7 for him. Since there is no distribution to the partners and the company was operating under a loss for 2019,  could I assume there won’t be withholding filing needed for the foreign partner?

Thanks a lot for your help