Desu vs Desu =P

I'm a beginner to Japanese as a whole in terms of speaking it myself. I've watched a lot of anime and seen it in the grammar studies too, why is desu sometimes said fully and sometimes not?

ie: Hai, totemo amai desu. In the practice part desu is pronounced De+Su
yet here: Tanoshii desu. In the practice part here it is just pronounced Des.

This has been very confusing to me. If anyone can help me it would be great. :)

Hi CharlesC22さん!

Usually,「です」is not spoken in full and is pronounced as "des". However, sometimes it is spoken in full, as "de-su", to add an emphasis. This is quite common in anime, especially for characters who are trying to use a cute manner of speech.

I hope that helps. Please do not hesitate to ask if you have any other questions :)
がんばってくださいね！

Crystal