Oussama... there are four possible uses of "as...as". I could copy and paste them here, but it would be better for you to look at the website: http://dictionary.cambridge.org/grammar/british-grammar/as-as Send a message or comment if you do not understand something in the website... bon chance

We use "as ... as" to make comparisons when the things we are comparing are equal in some way. "The weather this summer is >as bad as< last year." Remember there's the negative form "not as .... as". We use this to make comparisons between things which aren’t equal. "She’s >not< singing >as loudly as< she can." Note: I see this mistake often: "as same as". This is NOT correct. By using 'same' you are already doing some sort of comparison, which means it's a double comparison.