In fact, purchasing a new car while you're already behind on payments on another car could worsen your financial situation and make the repossession more likely. The lender repossessing your car might see the new purchase as an attempt to defraud them.
To avoid repossession, you need to address the underlying issue: the debt on your existing car. Contacting your lender immediately to discuss options like a repayment plan or surrendering the vehicle is crucial. Ignoring the problem will almost certainly lead to repossession, and buying a new car won't change that.