Alternative pluperfect forms

There are two other forms of pluperfect, both are colloquial.

1. This form is made by adding suffix   -idi to the past base.

Verb stem + past ending [ -di,dı,du,dü ] + idi [udu,üdü ] + Personal suffix 

- Baktı + idi + m ---> Baktıydım. [ one vowel is dropped & takes buffer "y" ]

 [ I had looked ]

  - Gitti + idi  --->  Gittiydi

 [ He/She had gone ]

  - Gördü + idi + k ---> Gördüydük  [ -idi changes into -üdü due to vowel harmony ]

  [ We had seen ]

   - Çalıştı + idi + n  ----> Çalıştıydın.

  [ You had worked [studied]

  2. This form is made by moving person between two suffixes.

 Verb stem + past ending + Personal suffix  +  di [du,dü ]

   Git     +  ti    +  m   +  di  ---> Gittimdi  [ I had gone ]

   Gör  +  dü  +  k  +  tü   ----> Gördüktü [ We had seen ]

   Bil   +  di   +  y + di  ---> Bildiydi [ He had known ]

   Kal  + dı + n + dı  ----> Kaldındı   [ You had stayed ]

* Note : Those are the forms that can be heard in colloqual speech.

 Therefore Its better to stick with the common form - mIştı.

Git + mişti + m ---> I had gone

Gör  + müştü + k  ---> We had seen

Bil   + mişti   ----> He had known

Both ( gittiydim ve gittim di) mean the same, don´t they?

Yes, they both mean the same thing which is  " I had gone "

However,  I would recommend you to use  the common form --->-mIştI  [ gitmiştim ]