How to explain for my daughter that $\frac {2}{3}$ is greater than $\frac {3}{5}$? I was really upset while I was trying to explain for my daughter that $\frac 23$ is greater than $\frac 35$ and she always claimed that $(3$ is greater than $2$ and $5$ is greater than $3)$ then $\frac 35$ must be greater than $\frac 23$.
At this stage she can't calculate the decimal so that she can't realize that $(\frac 23 = 0.66$ and $\frac 35 = 0.6).$
She is $8$ years old.

It's quite impressive that an 8-year old can state a clear reason (even if wrong) for a mathematical conclusion. I suggest you should be pleased rather than upset, and should begin with the respectful approach of addressing her reasoning.
So you might try asking her which is the greater of $1/3$ and $2/5$.  If she chooses $2/5$ you might then explore with her the implication that:
$$3/5 + 2/5 > 2/3 + 1/3$$
when in fact:
$$3/5 + 2/5 = 1 = 2/3 + 1/3$$
If that proves unpersuasive I would suggest representing fractions as sections of a straight line (rather than of rectangles, circles, cakes etc which introduce further complications).  So draw (or perhaps ask her to draw) a line of (for convenience) $15$ cm and mark against it the thirds (every $5$ cm) and fifths (every $3$ cm).  You can then ask whether the line section representing $3/5$ is longer than that representing $2/3$.
