It shouldn't take 30 seconds to create a client or do most anything in the system. That long of a wait time can usually be attributed to latency or server performance issues.
As mentioned above, you may not have enough system memory available and the server could be paging a lot, reducing performance and response time. You didn't mention whether you're on a VPS, but if so, you could be low on resources or the server could be overloaded, causing the issue. If the database server is different from your Blesta server, there could be latency issues or stalled/long-running queries that are causing the slowness with some actions. It's difficult to say exactly where the cause lies, but in any case you should take a look at the server resources and update its configuration as necessary.