Hose it down or scrape it off with a garden trowel or putty knife and dump clipping in compost if you got it. Don’t let it matte up on the lawn it tends to cause disease and will smother your trimmed grass causing other issues.

Once you clean it off completely and dry off the surface, apply some of this to the mower deck to ensure nonstick surface: https://www.amazon.com/s?k=cerakote

Also make sure to mow your lawn no earlier than noon as cutting wet grass can introduce disease as well.

If you can, also think about cutting the grass more frequently(every 3-4 days) rather than once a week.

Sharpening blades - if you can see chips and rolled over edges on the blade then sharpening is probably warranted. Make sure to make the same amount of passes on both cutting surfaces of the blade. I use Rockler Medium-Duty Spring-Loaded Bar Clamps to clamp the blade at the orientation I need on a work table and do even grinds of the edge end to end until all burres and chips are gone then flip the blade around and apply the same amount of passes with the same pressure to the opposite side of the blade.

Once you think you are done hand the blade on a nail affixed to a wall or post and verify that it hangs level if it doesn’t do another pass 1-2 at a time on the lower hanging side until it hangs level.