In this case you would better not to use the name you have chosen.
If the name is in the Trademarks Register but not in the Business Register, the name is then protected for certain products and/or services and you may not use it any more for those specific products and/or services. If the trademark concerned is a very well-known one, it often does not even matter whether it has been registered for the same products and/or services. It is in any case better to avoid using very well-known brand names.
If the name is in the Business Register but not in the Trademarks Register, and the trade name is being used in the same region in which you are active, and for the same activities and services, you should choose a different name.
You should also take into account that there are no purely descriptive names in the Trademarks Register. This is because to be registered a brand name, or trademark, cannot be descriptive for those products and services for which the trademark application is filed: ‘baker’ for a baker’s shop, for example. This sort of stand-alone brand name is refused by BOIP, and therefore no such names appear in the Trademarks Register.