If you wish to increase your pension contribution you can do so on the Pension Dashboard by increasing the amount and then selecting 'Update contribution'. Mintago is not able to give advice on how much you should up your pension contributions, however, the green line in your Retirement Planner graph will estimate the 'Target' pension contributions you'll need to make (both your contributions as an employee PLUS your employer's contributions) to achieve your 'Target retirement'.
As a rule of thumb, to understand how much you should be contributing, you can check the following formula:
Take the age you start your pension and halve it;
Put this % of your pre-taxed salary into your pension each year until you retire.
This means that by starting at age 28, one should aim to contribute at least 14% of their salary for the rest of their working life. This percentage also includes the employer’s contributions, so one will only have to fund the rest!