If you feel your lens isn't wide enough you probably want a wide-angle zoom. There are also wide-angle primes, but a zoom gives you more compositional choices, which is especially important for landscape photography and astrophotography. As far as I can tell there are only four wide angle zooms available for the micro 4/3 ecosystem: the Olympus 9-18mm f4-5.6, the 7-14mm f2.8 pro (the latter is faster, which may be an important consideration for the astrophotography), the Panasonic 7-14mm F4 and the 8-18mm F2.8-4. As for the macro lens the Olympus 60mm f2.8 macro seems to have very good reviews, so that might be something you can check out.

Disclamer: I don't own any of the above lenses, so my advice is based on the limited information I could find on the Internet.

My advice I would consider if you really need these, usually speciality lenses are more expensive then the general-purpose lenses, I would rent one and see if it is really necessary to buy it for your needs. Just to let you know, you could probably do astrophotography with the lens you already have, a lot of it is knowledge of camera settings and post-processing, although if you are really into that kind of photography you may get better results with a wider and faster lens. For the macro, there are tricks you can use to do macro photography with just about any old lens. As for the wide-angle you can stitch together a couple shots to emulate shooting with a very wide angle lens.