Let's take for example الحمد لله- The most common pronunciation is: Al-Hamdo-Li-Lah. Now, even-though there is a Shada/شَدّة on the word Allah, it is not emphasized. Why is that? Another example is بسم الله - most common ways of saying do not include the emphasis of the Shada on Allah and is said as Bismi-lah. Why?
The answer is taken from this source , and I will extract the general and main rule from it and format it as a short answer, for more details in Arabic get to the source
According to rules of Tajweed تجويد you can pronounce the (L - ل - لام) in the word Allah الله in 2 ways they are called (tafkheem تفخيم - ) and (ترقيق - tarqueeq)
- tafkheem means stress the letter and make it fat and show it. like you do when say qual Allah قَالَ الْلَّهُ
- tarqueeq means don't stress the letter and say it in a fine way. like you do when you say alhamdu lelah الْحَمْدُ لِلهِ
The general rule that you can apply on this letter (L- ل) in the word Allah , is that if the word Allah is preceded with (a - o / fath - dam /فتح - ضم) you make tafkheem example:
qual(a) Allah - قَالَ الْلَّهُ as in 5:116 or
muhammadon rasool(o) Allah مُحَمٌّدٌ رَسُولٌ الْلَّهِ as in 48:29
While if it is preceded by (e / kasrah / كسرة ) you make tarqueeq, example:
L(e) llahe لِـلَّهِ as in 2:284
a / o --------> tafkheem (Quala Allah / Al-Hamdo-Li-Lah)
e ------------> tarqueeq (Bismi-lah)
This is common with English speakers. English does not have a shaddah, and words with double letters are just said as if they were a single letter.
Say the words: letter better filler comment
you will have said le ter be ter fi ler co ment
let ter bet ter fil ler com ment
since you can't say shaddahs in English, such people, when speaking Arabic, miss the shaddah out and cannot say it. That is why English speakers say "A-Lah" and not "AL-Lah".