"This present is very nice, thank you very much!"
Translation:Bu hediye çok güzel, çok teşekkür ederim!
The noun after bu takes the accusative when it is direct object -- but the dative when it is the indirect object, the nominative when it is the subject, the ablative when it is the origin, etc. etc.
Case marking does not depend on bu except insofar that a direct object marked with bu is necessarily definite and therefore takes the accusative where an indefinite direct object would not. (For example, kitap okuyorum "I am reading books" (in general) versus bu kitabı okuyorum "I am reading this book".)
"This present is very nice, thank you very much". (Bu hediye çok güzel, çok teşekkür ederim).
To describe the present as being "very nice" could be interpreted as being just the opposite ... as in you really don't like the present, but feel obligated to thank the person who gave it to you! If genuine thanks (rather than sarcasm) is being conveyed for a gift that is actually appreciated, then the adjective "nice" leaves a lot to be desired! Any other word besides "nice" (lovely, beautiful, wonderful, fabulous) would have been preferable!