SharePoint Search

My SharePoint search is not working. I have a document library with 5000 entries. If I filter in two columns, I have about 200 search hits. However, if I use the independent Search Query Tool (https://github.com/pnp/PnP-Tools/tree/master/Solutions/SharePoint.Search.QueryTool) and specify this filter, I only get 15 search hits. I assume that the search index is not working properly. I have already restarted the indexing several times.