Meals for five days in Lisbon?

Well it will probably depend on where you are staying. My one suggestion is avoid the restaurants where they are standing outside to wave you in.
For breakfast I would stroll until i found an appealing little place and head there each day for my morning coffee
For lunch I would find a nice viewpoint ( miradouro) and find a little toasty shop and have a sandwich.

For dinner there are lots of good recommendations if you search. I like Clara's em Castillo and Le petit cafe . Both in the Alfama/ Castello area, but it has been quite a few years since I was there, so this is not a recent recommendation. Lots of people recommend the time out market.

That’s quite the broad ask.

I liked the Time Out Market. Lots of options.

https://www.timeout.com/time-out-market-lisboa/restaurants

My suggestion is to walk around and find a place that appeals to you. Far too often we’ve eaten at a restaurant that was good on one trip, but when we returned on a subsequent trip, it was a huge disappointment.

For convenience we get the hotel’s breakfast and we seldom eat lunch. While walking around my wife looks at menus to see if it might be a place she want to go and if it has an inviting atmosphere.

The restaurants I’ve mentioned below are located in the Baixa district, where we stay.

Not sure when you’re travelling but the fresh sardines are divine, when in season.

Taberna Da Baixa. Rua dos Fanqueiros, 161-163, Lisbon

Alternatively O Sopinhas. Rua da Madalena 50, Lisbon

If you feel like a change from Portuguese food we’ve dined at Prima Pasta for many years. Rua da Madalena 27, Lisbon.
Predominantly locals at lunch time. You need to reserve a table, or dine early in the evening. Very well priced simple Italian fare. Always consistent.