[Kausilwf]

You asked two separate questions:

A)What is the correct concept of 1) 'fear of Allah' and 2)Trust in Allah?

and

B)How to invest 40k-50k.


A1)

Here are two articles by Shaykh al Oudah regarding fear in life.

The Feeling of Fear part 1

The Feeling of Fear part 2

From article two:
Some scholars of spiritual matters have correctly observed: “The most complete state that a person can be in is a perfect balance between hope and fear.”

Ahmad b. Hanbal used to say: “A person’s hope and fear should be equal.”


Which is superior, fear of Allah Himself or fear of sin?

The answer to this is that the fear of Allah is superior, for even a person who is free from sin will feel this fear. Allah says, speaking about the Prophets (peace be upon them):

“They call upon their Lord in fear and hope.” [Sûrah al-Sajdah: 16]

“Verily, they used to hasten to perform good deeds and used to call upon their Lord in hope and dread and they had humility before Us.” [Sûrah al-Anbiyâ’: 90]

Allah tells us that this is the reason for salvation. He says: “This is for him who fears standing before Me and fears my threat.” [Sûrah Ibrâhîm: 14] This verse is talking about the most select and pious of people. Their status in Paradise will be elevated on account of their fear of Allah.


Regarding anxiety:

Ibn Jawzî said: “I was plagued by a problem that compelled me to continuously suffer from worry and anxiety. I began to go to great lengths trying to figure out any ruse or strategy to rid myself of that problem, but to absolutely no avail. Then I remembered the verse: “And whoever fears Allah, Allah will provide for him a way out.” Then I realized that fear of Allah is a way out of every worry. No sooner did I resolve to strengthen my fear of Allah than I found a way to solve my problems.”