What to do with existing trees when establishing a permaculture garden

Greetings!

I have recently moved into a home with a garden after many years of apartment jumping.

The garden is a dream for me!I now have a lawn space bordered with trees, shrubs and bushes.

I want to introduce fruit species along the border. However, that space is already taken up.

The existing trees as shown, are established and cast a lot of shade on the area.

1) What is the impact of removing the trees? On the soil specifically… 2) I am not too keen on cutting them down, would thinning them out be an option to allow more sunlight? If I plant fruit species in between existing trees – will there be too much nutrient competition? Will the fruit trees thrive with dappled sunlight?

I am in Johannesburg, South Africa.

Any other comments or tips are appreciated.

Thank you!