asset image not appearing in flutter

I am using dhiwise to convert my figma prototype into flutter but the header is not appearing and is somehow above the screen. I tried moving it elsewhere but it just puts it outside the header.

current look
what it is supposed to look like

return SafeArea(
 child: Scaffold(
 backgroundColor: ColorConstant.whiteA700,
 body: Container(
 height: size.height,
 width: size.width,
 child: Stack(
 children: [
 Align(
 alignment: Alignment.center,
 child: SingleChildScrollView(
 child: Container(
 height: size.height,
 width: size.width,
 child: Stack(
 alignment: Alignment.topRight,
 children: [
 Align(
 alignment: Alignment.center,
 child: Container(
 height: size.height,
 width: size.width,
 decoration: BoxDecoration(
 color: ColorConstant.whiteA700,
 ),
 child: Stack(
 alignment: Alignment.bottomCenter,
 children: [
 Align(
 alignment: Alignment.topCenter,
 child: Container(
 width: size.width,
 padding: getPadding(
 left: 11,
 top: 7,
 right: 11,
 bottom: 7,
 ),
 decoration: BoxDecoration(
 color: ColorConstant.blue200,
 ),
 child: Column(
 mainAxisSize: MainAxisSize.min,
 crossAxisAlignment:
 CrossAxisAlignment.start,
 mainAxisAlignment:
 MainAxisAlignment.start,
 children: [
 CustomIconButton(
 height: 53,
 width: 53,
 margin: getMargin(
 bottom: 276,
 ),
 child: CustomImageView(
 svgPath: ImageConstant.imgUser,

the custom image view code, this code was directly from the website itself and I have no idea what any of the code means to do

// ignore_for_file: must_be_immutable

import 'dart:io';

import 'package:cached_network_image/cached_network_image.dart';
import 'package:flutter/material.dart';
import 'package:flutter_svg/flutter_svg.dart';

class CustomImageView extends StatelessWidget {
  ///[url] is required parameter for fetching network image
  String? url;

  ///[imagePath] is required parameter for showing png,jpg,etc image
  String? imagePath;

  ///[svgPath] is required parameter for showing svg image
  String? svgPath;

  ///[file] is required parameter for fetching image file
  File? file;

  double? height;
  double? width;
  Color? color;
  BoxFit? fit;
  final String placeHolder;
  Alignment? alignment;
  VoidCallback? onTap;
  EdgeInsetsGeometry? margin;
  BorderRadius? radius;
  BoxBorder? border;

  ///a [CustomImageView] it can be used for showing any type of images
  /// it will shows the placeholder image if image is not found on network image
  CustomImageView({
    this.url,
    this.imagePath,
    this.svgPath,
    this.file,
    this.height,
    this.width,
    this.color,
    this.fit,
    this.alignment,
    this.onTap,
    this.radius,
    this.margin,
    this.border,
    this.placeHolder = 'assets/images/image_not_found.png',
  });

  @override
  Widget build(BuildContext context) {
    return alignment != null
        ? Align(
      alignment: alignment!,
      child: _buildWidget(),
    )
        : _buildWidget();
  }

  Widget _buildWidget() {
    return Padding(
      padding: margin ?? EdgeInsets.zero,
      child: InkWell(
        onTap: onTap,
        child: _buildCircleImage(),
      ),
    );
  }

  ///build the image with border radius
  _buildCircleImage() {
    if(radius!=null) {
      return ClipRRect(
        borderRadius: radius,
        child: _buildImageWithBorder(),
      );
    }
    else{
      return _buildImageWithBorder();
    }
  }

  ///build the image with border and border radius style
  _buildImageWithBorder(){
    if(border!=null) {
      return Container(
        decoration: BoxDecoration(
          border: border,
          borderRadius: radius,
        ),
        child: _buildImageView(),
      );
    }else{
      return _buildImageView();
    }
  }

  Widget _buildImageView() {
    if (svgPath != null && svgPath!.isNotEmpty) {
      return Container(
        height: height,
        width: width,
        child: SvgPicture.asset(
          svgPath!,
          height: height,
          width: width,
          fit: fit ?? BoxFit.contain,
          color: color,
        ),
      );
    } else if (file != null && file!.path.isNotEmpty) {
      return Image.file(
        file!,
        height: height,
        width: width,
        fit: fit ?? BoxFit.cover,
        color: color,
      );
    } else if (url != null && url!.isNotEmpty) {
      return CachedNetworkImage(
        height: height,
        width: width,
        fit: fit,
        imageUrl: url!,
        color: color,
        placeholder: (context, url) => Container(
          height: 30,
          width: 30,
          child: LinearProgressIndicator(
            color: Colors.grey.shade200,
            backgroundColor: Colors.grey.shade100,
          ),
        ),
        errorWidget: (context, url, error) => Image.asset(
          placeHolder,
          height: height,
          width: width,
          fit: fit ?? BoxFit.cover,
        ),
      );
    } else if (imagePath != null && imagePath!.isNotEmpty) {
      return Image.asset(
        imagePath!,
        height: height,
        width: width,
        fit: fit ?? BoxFit.cover,
        color: color,
      );
    }
    return SizedBox();
  }
}