If the sample has more than about a half inch of what appears to be matted straw, then it is time to de-thatch your lawn. The best time to de-thatch your lawn is in late summer or early fall. If this isn't possible, the next best time to de-thatch your lawn is in the spring. Reseed your lawn immediately after using the verticutter. Make sure the type of grass you select is suited to your conditions.
All turf grass prefers full sun.
However, some grass will tolerate shade better than others. A blend of perennial rye grass and fescue tolerates shade the best. Like most plants, turf grass benefits from well-drained rich soil. Remove your existing grass and enrich your soil. If your soil is acidic apply lime before you seed or sod.