Customizing search

Hi

I am creating a custom WP theme, I have an advanced search feature whose code is below:

******************* start of code **********************
<form role=”search” method=”get” id=”searchform” class=”searchform sidebar-search-form” action=”<?php echo home_url(‘/’); ?>”>
<?php wp_dropdown_categories(‘show_count=1&hierarchical=1&depth=2&show_option_all=Any Make or Model’); ?>

<select id=”exterior_color” name=”exterior_color” size=”” title=”Exterior Color”>
<option selected disabled value=”any”>Exterior Color</option>
<option value=”Red”>Red</option>
<option value=”Green”>Green</option>
<option value=”Blue”>Blue</option>
<option value=”Yellow”>Yellow</option>
<option value=”White”>White</option>
<option value=”Black”>Black</option>
</select>

<select id=”model_era” name=”model_era” size=”” title=”Model Era”>
<option selected disabled value=”any model of”>Model Era</option>
<option value=”1940,1941,1942,1943,1944,1945,1946,1947,1948,1949″>1940s</option>
<option value=”1950,1951,1952,1953,1954,1955,1956,1957,1958,1959″>1950s</option>
<option value=”1960,1961,1962,1963,1964,1965,1966,1967,1968,1969″>1960s</option>
<option value=”1970,1971,1972,1973,1974,1975,1976,1977,1978,1979″>1970s</option>
<option value=”1980,1981,1982,1983,1984,1985,1986,1987,1988,1989″>1980s</option>
<option value=”1990,1991,1992,1993,1994,1995,1996,1997,1998,1999″>1990s</option>
</select>

<input type=”submit” class=”btn btn-default” id=”searchsubmit” value=”Search    →” />

</form>

******************* end of code **********************

I am having few issues in above search.

1. It is submitting to homepage, when a category is selected from dropdown, it gives the result on category.php, if more parameters are selected, it doesn’t gives correct results and takes me to homepage
2. Model era dropdown is based on one decade, so that will be a range of years, I dont know how to do that in form and link to search among custom fields
3. I am using advanced custom fields, so the color and model era will search from those custom fields

Can anybody help me on my search form please? Also I need php code for search result page.

Thanks.