Problems with rdlc reports

Question

I am developing a desktop application in C# application, I have some problems with Microsoft visual studio 2013 reports, the problems are :  - some reports are slow   - some reports have a problem with vertical spacing between textboxes, I haved used the rectangle tool to fix this problem and it gives good results specially when press "Print Layout" and when exporting to pdf, but still some incorrect vertical spacing between textboxes exist in normal operation, all problems disappear in printing the reports, but in normal operation some are existed, I am self learning programming, I would be very appreciated for help, thanks.