How to put new element under previos?

I am making like-whatsapp chat on ESP32+TFT display.
What I did? I have the varable msg_y (total heights of all elements) which equals 0 without messages. I create an object for message every time I receive or send message
lv_obj_t * incoming_message = lv_obj_create(ui_Screen1);
lv_obj_set_width(incoming_message, 200);
lv_obj_set_height(incoming_message, LV_SIZE_CONTENT);
lv_obj_set_x(incoming_message, 0);
lv_obj_set_y(incoming_message, msg_y);
lv_obj_t * incoming_message_text = lv_label_create(incoming_message);
lv_obj_set_width(incoming_message_text, lv_pct(100));
lv_obj_set_height(incoming_message_text, LV_SIZE_CONTENT); // the height equals text’s height
lv_label_set_text(incoming_message_text, “Hello!”);
msg_y = msg_y + lv_obj_get_height(incoming_message) + 20;

The last string increases msg_y with element’s height and 20 pixels more. So, if the first message has y coordinate 0 and message’s height is 80 px, the second message should start with 100 pixels (under 1st message) and it start on 20 pixels.

So, I found out that construction like

int32_t a = lv_obj_get_height(incoming_message);
returns zero.

And another question. How to scroll the main screen automatically yo the last element?

Just need to set width. Without setting width every element has height 0px.
And to scroll to the last element I used:
lv_obj_scroll_to_y(obj, y, LV_ANIM_ON);