Hi!
Just to add to Andrei's advice, I thought I'd share my past experiences with strengths-based interview questions!
For these types of of questions, the important element is to answer truthfully and be yourself. They are typically looking to see how you would handle specific problems, your general working style, and the traits that you naturally possess that would make you a good fit for the firm. In preparation for the interview, I would make a note of what your key strengths are, and how they align with the skills needed to be a trainee (and what the role involves).
If you are given a hypothetical scenario, I'd talk the interviewer through each step that you would take to address the situation, and how you would use your personal strengths to aid you in handling anything that comes up.
Additionally, I've also found that the questions can be reflective in nature and may ask you specific questions about your way of workings. For an interview I did on a vacation scheme, I was asked "What type of person are you under pressure?" (which definitely threw me off!). There isn't necessarily one right answer here, and I would take a moment to actually think your answer through and consider how you usually approach these situations. It might be helpful to reflect on your past experiences and weave these into your answer, so that the interviewer can see that you are rooting your answer in concrete examples.
I hope that helps!
