Do the profits generated from a private capital commercial transaction, which falls outside the scope of activities agreed upon with the partners, become entirely the right of the questioner?

Since the activity was outside the official working hours of the two companies and with your private funds, there is no sin upon you in engaging in it. You alone are entitled to its profits or bear its losses, whether the activity was similar or dissimilar to the activity of the two companies. A company does not prevent a partner from disposing of their time and private funds. Al-Ramli said in Nihayat al-Muhtaj: "(And if) a partner (bought something and said, 'I bought it for the company,' or 'for myself,' and the other partner denied him, the buyer is to be believed) by his oath, because he knows his intention best, whether he claimed to have stated it explicitly or merely intended it."