Learn Turkish: Aslında bu kolay değil. - Actually this is not easy.

It comes from the word asıl (meaning 'essence' or 'origin'). It takes the possessive ending -ı (its essence), the buffer letter -n-, and the locative case -da (in). So it literally means 'in its essence'!

Why doesn't the sentence end with değildir to mean 'is not'?

In everyday spoken or written Turkish, the 'is' ending (-dir) is usually dropped for simple, personal facts. You would only say kolay değildir if you were making a very formal, general statement, like in a textbook or a lecture.

Could I put bu at the very beginning of the sentence?

Yes, you can absolutely say Bu aslında kolay değil. Turkish word order is flexible. Putting aslında at the front just puts slightly more emphasis on the word 'Actually' in the conversation.

How would I change this sentence to say 'Actually this was not easy'?

You would add the past tense suffix for the verb 'to be' (-di) directly to the negative word değil. The sentence would become Aslında bu kolay değildi.