If you have 25k assets you're well over the recommended asset count for an SQL Compact database, which is about 5k. Though you indicate that your database size is 6GB~ while the SQL Compact size limit is actually 4GB, you may already be running an SQL Server database, express edition, which is limited to 10GB. You can check which database edition you're using under Configuration\Database Scripts.
If you are still running an SQL Compact database, you can migrate to SQL Server using
this article. Make sure you're running
the latest Lansweeper version (6.0.0.51) prior to migrating.
When you use an SQL Server database, it is possible to split your
components (web console, scanning service and database) between multiple servers, that should already provide a performance increase. You can check if your license allows multiple scanning servers under Configuration\Your Lansweeper License. If there is no mention of a scanning server above your asset limit, you'll be limited to a single scanning server. If you wish to upgrade your license to allow for multiple scanning servers you can contact our sales department for this (https://www.lansweeper.com/contact-sales/).