Tax filing

Hello.

does the FOD help in filing taxes ? can i got there and get some help as I dont speak Dutch or French

Yes it does, google "aide a la declaration des impots " or something similar. However, more than half the free clinics have taken place already, they started at the beginning of May.

thanks for the input. i was able to visit the FAC in Leuven and they did help in filing for taxes for 2015 (taxonweb). Since I got married in May 2015, I had a tax break and started to get around 300 euro more in my net salary. However, the tax authorities said I am still being considered as single and need to repay that amount indicating that i have not paid enough tax - hence I need to pay back 1800 Euro to the government - has anyone faced similar issue ?

For 2015 you will indeed be considered single and married from 2016.
If you have to pay, you ask the payment office - bureau des recettes in French, sorry don't know name in Dutch - for the ability to pay in 12 month installments. Just explain you cannot pay all at one time because of the unexpected nature of bill, they are usually quite understanding. But you MUST pay.
I had to take out a loan to pay my unexpected tax bill so I know how it feels, mine was a whole month's income.