All the coins you hold are good, but lately ADA and DOT have not developed good prices, even ADA is called a stable coin, while DOT has very good technological development but has no effect on current market prices, although in the future the two coins can still develop better , that's just my opinion and do your own research.
ADA is not a stable coin in any way at all, it is volatile, the value in the market fluctuates from one price to another. The price has been dropping and that’s why I would say he should sell it now and wait for another time to invest or he can just wait for another time because it has already decreased much, don’t you think so? Selling now might be a loss for him, so it is something that should have been done for long time ago.
The value can still increase in the future because the coin is a really good one and there is no doubt that it has so many good opportunities to go high in the future. Same thing with Polkadot. Overall, the sentiment toward cardano is too good right now; hence instead of selling it, making use of currently available dips will help any crypto investors in long run.