Error (10500):VHDL syntax error at cqg.vhd(31) near text ":=

Error (10500):VHDL syntax error at cqg.vhd(31) near text ":="; expecting "then"
Error (10500):VHDL syntax error at cqg.vhd(31) near text ":="; expecting "then"
Error (10500):VHDL syntax error at cqg.vhd(33) near text "elsif"; expecting "end",or "(",or an identifier ("elsif" is a reserved keyword),or a sequential statement
Error (10500):VHDL syntax error at cqg.vhd(35) near text "if"; expecting "case"
library ieee;
use ieee.std_logic_1164.all;
entity cqg is
port(clk,reset:in std_logic;
x:in std_logic_vector(1 downto 0);
sum_int:out std_logic_vector(3 downto 0);
sum_dec:out std_logic_vector(3 downto 0));
end cqg;
architecture behave of cqg is
type states is(s0,s1,s2);
signal current_state,next_state:states;
variable i1:std_logic_vector(3 downto 0);
variable d1:std_logic_vector(3 downto 0);
begin
reg:process(reset,clk)
begin
if clk'event and clk='1' then
if reset='1' then current_state