Is this saying correct for bitcoin, or not?
Bitcoin have no inflation, so the bitcoins should not work?
In the end, Bitcoin will have no inflation, but at the moment the supply is inflating by 50 BTC approximately every 10 minutes. Every 4 years, this is halved to 25, 12.5, etc until it reaches the limit of Bitcoin precision and becomes 0. But, regarding your question, once Bitcoin is non inflationary, it will still be profitable to put it to work. The currency will lose it's value if no one trades it, which is the same as inflation. But, with Bitcoin, the inflation/deflation is ultimately controlled by the demand for Bitcoin.