How are you integrating Magento with Typo3? With a third-party extension?
IMHO Magento itself is a very powerful CMS so there's no need to include another CMS like Typo3.
As for the slow loading, it can be a combination of multiple problems, one of it being Magento + Typo3.
To quote what I have stated in another topic:-
1. Are you using any extensions that can slow things down (this is very normal and happens all the time)? Use the Magento profiler to identify any problematic extensions.
2. Are your Magento logs regularly cleaned? Make sure that Log Cleaning is enabled (and the Cron Job is running) as the logs can make your database bloated which will slow things down.
3. Are all application level optimizations already performed? Things like enabling Magento cache, GZip compression, etc.
4. As for the server or hosting level, is the server properly optimized for Magento? Is the MySQL properly tweaked to match your store? --> This is obviously a problem as well if the site is hosted on a budget hosting service.
