One thought you may want to keep in mind is to incorporate more permanent plant types into the bed. While a selection of perennials will certainly return each year, they do disappear in winter, leaving the bed a blank hole for many months. Personally, I consider this a highly undesirable feature in an area that is so conspicuous and open to public view. Incorportaing a few smaller growing shrubs or dwarf evergreens would provide a far more permanent structure (i.e., "bones") that would provide interest during the off-season as well. There are a few hardy perennials that will provide a more evergreen presence also, and an assortment of groundcovers that offer this feature too. Some other ideas to consider: reconfigure the bed to a more naturalistic shape - a rectangular bed plunked down in the middle of an expanse of lawn looks unconnected and awkward. Get rid of the little strip of lawn running between the sidewalk and the planting bed - it serves no purpose and increases the maintenance. And perhaps mound the soil slightly and include a few landscape boulders to offer some context as well as permanence - small shrubs, low spreading perenenials and ornamental grasses look especially good creeping or cascading around these rocks. And don't rely solely on flowers to achieve results. Flowers - even those provided by so-called long blooming perennials - are very temporary. Look for a contrast of plant forms, textures and attractive foliage to provided much more long term interest than just flowers can provide.

The flower saya "Lantana", but the leaves look more like a sedum. Does anyone know a lantana-like plant?

I think you've hit it. I knew it had to be some kind of Verbenaceae. Thanks!

Get a soil test, or more than one in view of the size of the plot. Then you know what you're dealing with. What kind of soil is it? Clay, silt, ... ? The soil test will tell you nutrient and organic matter content and pH. Armed with all that you will know how to amend. The soil type and organic matter content will suggest whether you need to add organic matter and the best ways to do that. I suspect you'll need compost unless this was already a feedlot or something. In which case, start looking for sources of cheap or free compost, manure, etc.