Aiming a 200kcal TDEE, but I get tired from workouts pretty quickly. Any tips?

My current calorie intake: 1600kcal

H: 5'1

W: 50.5kg

My workout routine:

-combo of walking and stair climbing for two hours 5 times a week

-on te rest on the week i just do walking

-I do lift weights but only doing one exercice to tone my triceps.

I want to increase my TDEE to 2000kcal but I already get tired at 1600kcal due to the exercice, despite those exercices only burning 400kcal max (according to the app)

My intuition is that i do need more strength training, but what (home) exercice i can do to mitigate that fast exhaustion ?

Thank you in advance