If your specific issues are due to muscular weaknesses, yes. If it's due to reduced flexibility, then no. Chances are it'll be a bit of both.

Try bending over with your back in a slight upwards arch while keeping your legs completely straight and together.

Can you get below 90 degrees? If not, your flexibility along your posterior chain is poor. Can you effortlessly reach your toes with your fingers (you can bend your back this time)? If not, same.

Strength training alone won't fix those. And in fact, that poor flexibility will make it very hard to maintain proper form when lifting weights, and you're putting yourself at greater risk of hurting yourself.

On the upside, only a couple of months of stretches is enough to see a substantial improvement.

It might happen. Usually though it doesn't fix the underlying dysfunctions (doesn't target the highly untreated and tight muscles in an isolated way). From personal experience (myself + the people I train(ed)): you end up with worse problems.

Once things get screwed up enough, you need pretty specialized exercises to correct it. My glutes barely engage anymore, so typical lifting and gym exercises don't work. You feel like a dork doing the clam at the gym, but it works.