How does one control his or her desires? Are there any techniques

One way is to reflect that Allah is present and sees your actions at all times.

Another way is to reflect on death often.

Use this dua that is found in the Holy Quran

I fractured my hand while playing cricket. If I enter the situation of janabat, how can i perform ghusl without using water? This plaster needs to be dry

You can do ghusl jabeera where while doing ghusl, you can wipe over that part which is bandaged similar as done in wudhu jabeera

I wanted to know if you are allowed to work on 21st Ramzan as I have been told it is not allowed

Yes it is permissible.

I have some questions about sexual activity during Ramadan.

If I sleep with my wife after Iftaar, is there a certain timeframe which I have to do Ghusl within?

And: if I have a sexual dream, do I have to do Ghusl before Dhuhr-prayer? If yes, what do I do if I wake up after the Dhuhr prayer has entered, and then realize I’ve had a wet dream?

Yes you must make ghusl janaba before dawn.

In second scenario if you have a wet dream in the day you need to make the ghusl janaba before you make salat whether you woke up before zuhr or after zuhr had entered.

If I’m texting with my wife, and we start talking and I later on feel something wet in my pants. Is my fasting still accepted? And is it necessary to do Ghusl or not?

If what you’re describing is pre-ejaculate then no it does not invalidate the fast or necessitate ghusl.

Can you please suggest a book regarding Khumus, which is dealing with all aspects and is in detail.

https://www.al-islam.org/khums-islamic-tax-sayyid-muhammad-rizvi

Do eyedrops used for medicinal purposes (eye diseases etc) invalidate the fast?

No those do not invalidate fasting

I have two questions that keep bothering me which are as follows:

1. Application of Khums. I am clear about the distribution part but I am not clear on which asset or property it is payable. I want a response that can be proved and substantiated by practices or sayings of Imams. Apparently Khums is defined in sura e Anfal which was revealed after jang e Badr and totally related to rights, responsibilities and duties during & after a war fought for Islam. As it appears khums is applicable only on war booty.

2. Taqleed : importance of Taqlid in Islam and its prove from the sayings of Rasul e khuda or imams. When it started and what is the history? How to find a right marja?

I would highly appreciate clarity.

These two reads should have the answers you are searching for and clarify the subject matter inshallah.

https://www.al-islam.org/khums-islamic-tax-sayyid-muhammad-rizvi

http://najaf.org/books/249/249.pdf

My family is making duaa for something for 1 year. We made all the kinds of duaa, prayers etc. Including duaa's which they say Allah will never refuse them. We tried EVERYTHING, but it didnt get accepted (we wanted a baby boy, but got a girl). We are still happy with her, but it confuses us why it became a girl, since the duaa we made said that Allah never refuses this Dua. What could be a reason that Allah didnt accept it? Did we too much, sins etc?

https://youtu.be/X4JVPVTmyus

We see that the mother of Maryam wanted a boy as well but Allah gave her a daughter who was Maryam.

https://www.al-islam.org/hayat-al-qulub-vol-1-allamah-muhammad-baqir-al-majlisi/account-maryam-mother-isa

In my working career, I know that I am working with some racist discriminated environment where people never appreciate your job but always condemning as if they are the best. Even though that, their expectation on me is high to complete all the task given and I did that. I always make a dua to ask Allah giving me way out from this situation. Can you please give some advice?

Just try to be the best at what you do inshallah. Don’t worry about others who are being judgmental of you without cause.