When trying to increase your leverage, you may be getting an error message telling you to increase your Risk Limit.
The Risk Limit for a specific trading pair is the extra margin that is required to keep a position open. The purpose of it is to reduce the risk associated with having a large position open.
The Risk Limit scales with position size - if your position size is small, the risk limit will also be small.
A Risk Limit of 0.1% for the BTC Perpetual Future implies that the initial margin requirements are 0.1% higher for each BTC position size.
A position with a size of 5 BTC will be required to satisfy an additional initial margin requirement of 0.1 * 5 = 0.5%. If the base initial margin requirement is 1%, this will make the total initial margin requirement 1.5%. With an initial margin requirement of 1.5% the trader can have a maximum leverage of 66.66x. If the trader then reduces his position size to less than 1 BTC, the trader now only needs to satisfy an initial margin requirement of 1% (which corresponds to 100x leverage).
To decrease your Risk Limit, simply decrease the size of your position. This will allow you to further increase your leverage.