Part shade, part sun is fine for many things. What's important is good overhead light. So, almost anything that will go in planters. Try plants which will survive when occasionally neglected (to take the pressure off you!), such as herbs - rosemary, lavender, thyme, in the sunnier bits, and for a tropical look, evergreen fatsia japonica, with its big palmate leaves, for the shade. But, with care, you'll be able to experiment, and I'd try some early spring colour, primroses in tubs, then later, some summer bedding, particularly geraniums (pelargoniums) which appreciate sun and won't object if left unwatered for a week. Worthy

if you can painting the cement white will make it a lot brighter as white is nearly as reflective as mirrors and it will make the cement look nicer and be a nice backdrop to show of the planting colours as it is nutral excuse my spelling .

Busy Lizzies (Impatiens wallerana) are also very showy, can take some drought, and bloom well in the shade--no direct sun needed. They are somewhat more frost tender than Pelargoniums, so you want to be sure that the last frost is done before planting them. Busy Lizzies are also often sold in 6-packs, while Pelargoniums are rarely sold in anything smaller than a 10 cm, which are generally more expensive per plant. Some annuals also grow easily from seed--a considerable savings! These include Balsam (Impatiens balsamina), Nasturtiums, Violas (Viola tricolor varieties and hybrids), Marigolds--both English (Calendula) and "French" (Tagetes patula)--Four O'Clock (Mirabilis jalapa), Sweet Alyssum (Lobularia maritima), and many others. I would need to look at a seed rack to jog my memory!