Is there a solution to put an end to thinking of worries during prayer?
Firstly, make ablution after the time for prayer begins and busy yourself with remembering Allah, The Exalted, before the iqaamah (start of prayer).In order to become humbly submissive during prayer, you must perform prayer in congregation. After the prayer ends, stay in your place and read the post-prayer remembrances (Adhkaar) and make supplication to Allah, The Exalted.
Is the marriage contract considered valid if concluded at home by the marriage official (Ma`zon)?
Yes, it is valid as long as it is registered at the court.
What is the ruling on water that contains ornamental fish — does it become impure on account of their waste?
All praise is due to Allah, and peace and blessings be upon our master the Messenger of Allah ﷺ.
The water in a pond containing ornamental fish is pure so long as it has not been altered, for a small amount of fish waste (rawth) is pardoned and overlooked — provided it does not change the water.
It is stated in Ḥāshiyat al-Jamal ʿalā Sharḥ al-Manhaj (Vol.1/P.178): "A small amount of hair from a non-edible animal is pardoned, as is a small amount of hair from a riding animal — on account of the hardship involved in avoiding it — and likewise a small amount of fish waste is pardoned, unless it alters the water." And Allah the Almighty knows best.
Does the intention (niyyah) of the principal (muwakkil) suffice for the sacrifice (dhabḥ) of the udhiyyah?
Praise be to Allah, and peace and blessings upon our master, the Messenger of Allah.
If a person appoints an agent (wakīl) to perform the slaughter (dhabḥ) on their behalf, the intention (niyyah) of the principal (the one appointing the agent) suffices, and there is no need for the agent to have this intention himself. In fact, even if the agent is unaware that he is performing the sacrifice on someone's behalf as an udhiyyah (sacrificial offering), this does not affect its validity. And Allah, the Most High, knows best.