When can I use قدر الله
I think it means 'God forbid'

When can I use it in Arabic?

Can I use it when someone tells me a sad story about illness or war?

Thanks everyone

Question

When can I use  قدر الله
I think it means 'God forbid'

When can I use it in Arabic?

Can I use it when someone tells me a sad story about illness or war?

Thanks everyone

Answer

Salam Claudia,
Actually since you asked about "God forbid" and its relation with "قدّر الله", it means exactly the opposite! 
God Forbid: God is not allowing something to happen.
قدّر الله: Allah/ God is allowing something to happen.

To make it equal to God forbid, you should add لا to it, like this: لا قدّر الله.
Let's say you want to use it with sickness and war, here how it's possible in this situation:
1. لو اشتعلت الحرب في البلاد لا قدّر الله، سنغادر إلى دولة أخرى: 
If war started in our country "God forbid", we would leave to another country.
2. لو أظهرت التحاليل الطبية إصابة الفتاة بالمرض لا قدّر الله، سأقنعها بأن تبدأ العلاج فورًا:
If medical tests showed that the girl is sick "God forbid", I would convince her to start treatment right away.

Now if you want to use the opposite (قدّر الله/ God Allow) in those situations, look at these 2 sentences:
1. قدّر الله أننا كنا خارج البلاد عندما اشتعلت الحرب: 
Allah/ God allowed that we were out of the country when the war started.
2. قدّر الله أن تحاليل الفتاة الطبية أظهرت خلوها من أي مرض:
Allah/ God allowed that the girl's medical tests showed that she's not sick at all.

I hope this helps :)

Answer

As far as I know,
قدر الله وماشاء فعل means "Allah has decreed it and what He willed has happened". Simply, it means Allah wanted something to happen to you. So, In Islam we should be pleased with Allah whatever happens to us. For example, if you are sick we say the sentence. If you are in a trouble, we say it. We say the sentence with bad and good things, from our point of view,  that happen in our lives. In Islam, we believe that everything happens to us is from Allah whatever it is good or not. So we should be blessed.

Answer

sickness :  نقول  في العربية 
 (( شَفاكَ اللهُ وعافاك ))
Calamity or a problem or an accident or loss of something :
( قَدَّرَ الله وما شاء فعل )
In joy and congratulations: 
بارك الله لكم 
Many in the Arabic language  :))

Answer

know,
قدر الله وماشاء فعل means "Allah has decreed it and what He willed has happened". Simply, it means Allah wanted something to happen to you. So, In Islam we should be pleased with Allah whatever happens to us. For example, if you are sick we say the sentence. If you are in a trouble