This is the 194th most frequent Chinese word.
不少
"Quite a few" or "a lot."
In this case, '不少 (bù shǎo)' conveys the meaning of a considerable number, describing the quantity of problems solved.
通过努力，他解决了不少问题。
Through his efforts, he solved many problems.
In this sentence, '不少 (bù shǎo)' means 'quite a few' and is used to emphasize the considerable quantity of tourists in the park.
公园里有不少游客。
There are quite a few tourists in the park.
Here, '不少 (bù shǎo)' indicates a significant amount, referring to the time he spent preparing.