well when it comes to Arbic that's used in book which called فصحة ( fosha ) it differ somehow than arbic slang which is used by public 

when you meet someone in street you can say كيف حالك ؟ (keif halek ) but it would be alittle bit wired because it's not the slang that normal people use  so you can say ازيك ؟ (azyek ) 

and you can answer تمام - كويس so it's a slang 

if you want to say لا شيء which mean nothing you can say it ولا حاجة 

i watch tv ( انا بتفرج علي التلفزيون ) 

i want = عايز  in fosha it's اريد (ored )

today = اليوم (fosha ) = النهارده (slang )

yesterday = امس fosha = امبارح (slang )

tomorrow = غدا ( fosha ) = بكره (bokra -slang )

there is alot of words on that way you can ask about the slang of a sentence and i would with pleasure tell you

and finally don't annoy and distract yourself should i learn fosha or slang !!just go on your way and everything will come by practise as long as you are intersted  

To welcome someone in Arabic you can say مرحبا  (marhaban ) and usually you can say سلام (salam ) when mean peace 

when it's morning you can say صباح الخير (sabah alkheir ) which means Good morning 

when someone ask كيف حالك (keif halek ) which it means how are you you can answer جيد (gayed ) 

or بخير (bekheir )  

if you don't understand what someone says you can say أنا لا أفهم ( ana la afhem ) which mean i don't understand 

if he was talking in a fast way that you don't get words properly you can say تكلم ببطىء من فضلك ((takallam bibuṭ' min fadlak) which mean can you talk slowely 

when someone asks you about your hobbies he would say ما هي هواياتك (ma hia hwayatek ) which mean what's your hobbies 

there is some popular hobbies which can be used commenly 

السباحة (alsebaha ) =swimming 

التنس (tennis ) it's almost the same 

القراءة (alqera' ) reading 

السفر travelling (alsafar )

and if you would end the conversation you can say 

اراك لاحقا (arak la7qan ) see you soon 

سلام salam (peace )