Does sitting under the sun for too long affect ur skin?

Yes, yes, yes. Sun exposure increases wrinkles, skin discolorations, and your risk of skin cancer. It deceases elasticity and thickness of the skin...Just to name a few.
Burns, cancer risk. Excess sun exposure can harm the skin immediately (dry, itchy skin, or full sunburn) and over the long-term (more wrinkles, increased risk of skin cancers). The fairer your skin tone, the more sensitive you may be, but even very darkly pigmented skin can still be damaged by too much sun. Always use a good sunscreen (spf 15 or more) when enjoying the sunny outdoors, and you should be protected.