Learn Farsi: علاوه بر سرمایه، باید در مورد تقسیم کردن سهام شرکت مذاکره کنیم. - In addition to capital, we must negotiate about dividing the company's shares.

alaveh bar is a compound preposition meaning "in addition to". You do not add an ezafe after bar because it already functions to connect directly to the following noun, sarmayeh (capital).

Since the lesson is about fractions and division, how does the word saham (shares) fit in?

saham is an Arabic broken plural meaning "shares" or "stocks" of a company. Its singular form is sahm (share or portion). You will often see sahm used when talking about fractional portions of something.

Why is there an ezafe after the verb kardan in taqsim kardan-e saham?

In this sentence, the infinitive taqsim kardan (to divide) acts as a noun (a gerund), meaning "the dividing". When an infinitive acts as a noun and is followed by the thing being acted upon, they are connected with an ezafe (the -e sound), translating to "the dividing OF the shares".

Can I use darbare-ye instead of dar mored-e here?

Yes, you can. Both dar mored-e and darbare-ye mean "about" or "regarding" and are completely interchangeable. dar mored-e sounds slightly more formal and is very common in business contexts like this one.

Why is separated so far from ?