Shares in investment firm 3i Group gained on Thursday after the company said it delivered a "robust performance" in the first half, supported by a good flow of realisations and a strong balance sheet.The company, focused on private equity, infrastructure and debt management, recorded a total return of £234m in the six months to 30 September, compared with £175m in the first half of last year.However, it said that the macro and geopolitical landscape had deteriorated during the period, leading to increased volatility in currencies and other financial markets.Returns would have been greater, had it not been for a £73m adverse movement in foreign exchange mainly due to the strength of the pound against the euro.The group said the overall trading environment is "uncertain and volatile, with the Eurozone moving back towards recession and deflation and escalating conflict across the world". However, it assured it was taking a "cautious approach" to costs, gearing and new investment.Realisations totalled £324m in the first half, with a further £218m of proceeds received since the period-end.Net asset value per share increased to 358p by the end of the half, up 10p from six months earlier."We continue to seek new investment opportunities, but we recognise the increasing political uncertainty and stagnating growth in Europe and are mindful of the risks of over-paying for new investments in this environment," said chief executive Simon Borrows.