No. It is not correct.
The consumer on an indifference curve is willing to sacrifice less and less of commodity y to get an additional unit of commodity x.
is a better sentence in my opinion
There are no such expressions as less and lesser or lesser and lesser
The correct expression is less and less.
Also first time I have ever seen goods in singular. However it does exist in economics it seems. Note that the word good is not used in the description except once:
In economics, a good is a material that satisfies human wants and provides utility, for example, to a consumer making a purchase. A common distinction is made between 'goods' that are tangible property (also called goods) and services, which are non-physical. Commodities may be used as a synonym for economic goods but often refer to marketable raw materials and primary products.
Lastly (before your edit) I would expect on an indifference curve